sueop jungeneun hyudaeponeul sseuji malgo memohaseyo.

수업 중 means during class or in the middle of class.

• 수업 = class, lesson
• 중 = middle, during
• 에 marks the time/state
• 는 adds topic or contrast

So 수업 중에는 is something like:

• during class
• as for during class
• at least when class is going on

It sets the situation for the rest of the sentence.

The 는 adds a topical or slightly contrastive feeling.

Without 는, 수업 중에 just means during class in a neutral way.

With 는, 수업 중에는 can sound more like:

• during class, at least...
• when class is in session...

This often implies a contrast with other times. For example, the speaker may mean that using a phone is not okay during class, even if it might be okay at other times.

In Korean, 쓰다 often means to use something, not just to write.

So:

• 휴대폰을 쓰다 = to use a cellphone
• 돈을 쓰다 = to spend money
• 펜을 쓰다 = to use a pen

This is very normal Korean usage. Even though English usually says use a phone, Korean commonly says 휴대폰을 쓰다.

Both can refer to a cellphone in everyday Korean.

• 휴대폰 is a standard/native Korean term for mobile phone
• 핸드폰 is also very common in speech, even though it comes from English-like wording

In this sentence, 휴대폰 is completely natural and slightly more standard-looking, especially in notices, rules, or school-related language.

Because the sentence has two actions:

1. don’t use your phone
2. take notes

The pattern -지 말고 means:

• don’t do A, and instead do B
• rather than doing A, do B

So:

• 휴대폰을 쓰지 말고 메모하세요 = Don’t use your phone; take notes instead

If you said 쓰지 마세요, that would usually end the command by itself:

• 휴대폰을 쓰지 마세요. = Please don’t use your phone.

But here the speaker wants to connect that idea to another instruction, so -지 말고 is the right form.

Often, yes, but not always in a very strong instead of this, do that sense.

It usually connects two ideas like:

• don’t do A, do B
• rather than A, B
• not A, but B

In this sentence, the meaning is very natural as:

• Don’t use your phone; take notes instead

So -지 말고 is stronger and more purposeful than just saying two separate commands.

Both are possible.

• 메모하세요
• 메모를 하세요

Both mean please take notes or please make a memo/note.

Korean often turns a noun into a verb with 하다, and in many cases the object marker 를 is dropped when the noun + 하다 combination is very common.

So:

• 메모하다 = to take notes, to make a note
• 메모를 하다 = literally the same idea, just with the object marker shown

In instructions, 메모하세요 sounds very natural and efficient.

-하세요 is a polite command/request form.

It is commonly used when:

• speaking politely to students, customers, or the public
• giving classroom instructions
• writing notices or guidelines

It is polite but still clearly an instruction. In this sentence, it sounds like something a teacher might say to a class.

The subject is omitted, which is very normal in Korean.

The understood subject is you:

• You should not use your phone during class and should take notes.

Korean often leaves out subjects when they are obvious from context, especially in commands and instructions.

Because 휴대폰 is the object of 쓰다.

• 휴대폰을 쓰다 = use a cellphone

Here:

• 휴대폰 = object
• 을 = object marker

So 휴대폰을 simply shows what is being used.

Not well in this sentence.

• 안 쓰고 means not using or without using
• 쓰지 말고 means don’t use

That is a big difference.

안 쓰고 메모하세요 sounds more like describing a manner or condition, while 쓰지 말고 메모하세요 is a real prohibition plus instruction.

Since the speaker is telling someone not to do something, -지 말고 is the correct choice.

No, not especially.

Because of -세요, it is polite. But it is still a clear instruction, not a soft suggestion.

So it sounds like:

• polite
• direct
• appropriate for a teacher, school sign, or classroom rule

If someone wanted to sound softer, they might use a different expression, but for a classroom instruction, this sentence sounds natural and appropriate.

The sentence is built like this:

• 수업 중에는 = during class
• 휴대폰을 쓰지 말고 = don’t use your cellphone
• 메모하세요 = take notes

So the structure is basically:

During class, don’t do A; do B.

This is a very common Korean pattern for giving practical instructions.