kore ha muzukasii sentaku desu.

In this sentence, は is the topic particle. It marks これ as the thing the sentence is about:

• これ = this
• は = as for / speaking of

So これは means something like as for this or more naturally just this as the topic of the sentence.

Even though the character is written は, when it is used as a particle, it is pronounced wa. This is a special historical spelling that learners just have to memorize.

So:

• written: これは
• pronounced: kore wa

Japanese usually puts descriptive information before the noun it describes, and the main statement often comes at the end.

English:

• This is a difficult choice.

Japanese:

• これ は 難しい 選択 です。
• literally: As for this, difficult choice is.

A more natural English rearrangement is:

• This is a difficult choice.

So the word order is normal for Japanese:

1. topic: これ は
2. description + noun: 難しい 選択
3. polite ending: です

Because 難しい is an i-adjective, and in Japanese, adjectives normally come before the noun they modify.

So:

• 難しい選択 = difficult choice
• 大きい家 = big house
• 新しい本 = new book

This works a lot like English in this case, since English also says difficult choice, not choice difficult.

Because 難しい directly modifies 選択 as an adjective.

When an adjective describes a noun in Japanese, you usually just place it right before the noun:

• 難しい選択 = difficult choice
• 面白い映画 = interesting movie

No particle is needed between them.

です makes the sentence polite and completes the statement.

In this sentence:

• これは難しい選択です。

です is similar to the polite copula, often translated loosely as is, although it does not work exactly like English is in every situation.

Without です, the sentence becomes less polite or more casual:

• これは難しい選択だ。 = plain form
• これは難しい選択です。 = polite form

So です is mainly giving the sentence a polite, standard tone.

Yes. That is the plain, less formal version.

Compare:

• これは難しい選択です。 = polite
• これは難しい選択だ。 = plain / casual / firm

Both mean basically the same thing. The difference is tone:

• です is appropriate in polite conversation, class, business, and most learning materials
• だ is more casual and is often used in plain speech, writing, or stronger statements

Learners are usually taught です first because it is safer and more polite.

これ means this by itself.
この must be followed by a noun.

So:

• これ = this
• この選択 = this choice

That means both of these are possible, but they are structured differently:

• これは難しい選択です。 = This is a difficult choice.
• この選択は難しいです。 = This choice is difficult.

Both are natural, but they focus slightly differently.

They are very close in meaning, but the structure and focus are a little different.

1. これは難しい選択です。

   • This is a difficult choice.
   • It identifies this as a difficult choice.

2. この選択は難しいです。

   • This choice is difficult.
   • It talks about this choice and says it is difficult.

In many situations, the practical difference is small. But grammatically:

• 難しい選択 is a noun phrase: a difficult choice
• 難しいです is an adjective used as the main predicate: is difficult

Sometimes, but it changes the nuance.

• これは難しい選択です。 = As for this, it is a difficult choice.
• これが難しい選択です。 = This is the difficult choice.

Using は marks これ as the topic.
Using が tends to identify or emphasize this as the specific thing.

So これが難しい選択です might sound more like:

• This is the difficult choice
• This is the choice that is difficult
• This is the one in question

In a basic neutral statement, は is the more expected choice.

Yes, 選択 means choice or selection, and it is a normal word. It can be used in everyday situations, formal situations, and written language.

Examples:

• 難しい選択 = a difficult choice
• 選択する = to choose / to make a selection
• 選択肢 = options / choices

That said, in some conversations, Japanese may also use other words depending on context, such as expressions related to deciding or picking something. But 選択 is perfectly standard and natural here.

A simple pronunciation guide is:

• 難しい = muzukashii
• 選択 = sentaku
• です = desu

So the full sentence is:

• kore wa muzukashii sentaku desu

A few pronunciation notes:

• 難しい has four mora groups: mu-zu-ka-shii
• The shii part is held a little longer than a single shi
• です is often pronounced closer to des in casual actual speech, though learners are usually taught desu

Japanese does not have articles like English a, an, or the.

So 難しい選択 could mean:

• a difficult choice
• the difficult choice

The exact meaning depends on context.

In this sentence, English usually translates it as:

• This is a difficult choice.

The context tells us that a difficult choice is the natural interpretation.

No. In normal Japanese writing, spaces are usually not used between words.

So the standard written sentence is:

• これは難しい選択です。

Textbooks and beginner materials often add spaces to help learners see the parts more clearly:

• これ　は　難しい　選択　です。

That is just a learning aid.

難しい is an i-adjective.

You can tell because it ends in い in its dictionary form.

This matters because i-adjectives can directly modify nouns:

• 難しい選択 = difficult choice

They can also end a sentence directly:

• この選択は難しい。 = This choice is difficult.

This is different from na-adjectives, which need な before a noun:

• 静かな部屋 = a quiet room

So here, 難しい works exactly as expected for an i-adjective.

Yes, it is natural and correct.

• これは難しい選択です。

It sounds like a normal, polite statement and could be used in many contexts, such as discussing a decision, a dilemma, or a complicated situation.

Depending on context, a native speaker might also say things like:

• これは難しいですね。 = This is difficult, isn’t it?
• これは難しい選択だね。 = This is a difficult choice.

But the original sentence is completely natural.