watasitati ha kakutyouban wo erabi, tokuten wo kakuninsuru.

A natural reading is:

わたしたち は かくちょうばん を えらび、とくてん を かくにんする。

Word by word:

• 私たち = わたしたち
• は = pronounced わ here
• 拡張版 = かくちょうばん
• を = pronounced お
• 選び = えらび
• 得点 = とくてん
• 確認する = かくにんする

Also, the spaces are just for learners. Normal Japanese would usually be written more like:

私たちは拡張版を選び、得点を確認する。

は marks the topic of the sentence.

So 私たちは means something like:

• as for us
• we
• speaking of us

In English, we usually just say we, but in Japanese the topic marker は shows what the sentence is about.

So the structure is:

• 私たちは = as for us / we
• 拡張版を選び = choose the expanded version
• 得点を確認する = check the score

Yes, it could often be omitted.

Japanese frequently leaves out subjects when they are obvious from context. So in many real situations, you might simply say:

拡張版を選び、得点を確認する。

That can still mean We choose the expanded version and check the score, depending on context.

私たち is included here to make the subject explicit. This is common in learner sentences, instructions, or when the speaker wants to clearly contrast we with someone else.

拡張版 literally breaks down as:

• 拡張 = expansion / extension
• 版 = edition / version

So 拡張版 means something like:

• expanded version
• extended edition
• expansion version

The exact English translation depends on context. For example, it could refer to:

• a game edition
• a software version
• an extended release of something

A learner might also see バージョン used in Japanese. That is a loanword meaning version, but 版 is a very common native-style way to say edition/version in compounds.

を marks the direct object of a verb.

So:

• 拡張版を選ぶ = choose the expanded version
• 得点を確認する = check the score

In other words:

• what is being chosen? → 拡張版
• what is being checked? → 得点

English uses word order to show this, but Japanese uses particles like を.

選び is the stem of the verb 選ぶ.

Here it is being used to connect two actions:

• 選び、
• 確認する

This is a common written style meaning:

• choose ..., and then check ...
• choose ... and check ...

So:

• 選ぶ = dictionary form, to choose
• 選び = connecting form here

This kind of connection is especially common in formal writing, instructions, explanations, and summaries.

Only the final verb in the sentence needs to carry the main tense/style marking.

Here:

• 選び connects the first action
• 確認する finishes the sentence

So the pattern is basically:

Aを選び、Bを確認する。 = Choose A, and check B.

The final する makes the whole sentence plain, non-past style.

Depending on context, this can mean:

• a habitual action
• a general statement
• a future action
• an instruction-like description

Japanese dictionary form is not limited to literal present tense.

They are similar, but not exactly identical in style.

• 選び、確認する sounds more written, formal, or structured
• 選んで確認する sounds more everyday and conversational

Both can mean choose and check, but the nuance is different.

Compare:

• 拡張版を選び、得点を確認する。
  More formal, like written instructions or a manual

• 拡張版を選んで、得点を確認する。
  More natural in casual spoken explanation

So the sentence you were given has a slightly more formal or textbook-like feel.

The comma 、 helps separate the two linked actions and makes the sentence easier to read.

Japanese commas are often more flexible than English commas. Here it shows a pause between:

• choosing the expanded version
• checking the score

It is especially common when using this written connecting form:

• ～し、～する
• ～び、～する
• ～し、～を行う

So the comma is not mysterious grammar by itself; it mainly helps readability and structure.

得点 usually means:

• score
• points earned
• number of points obtained

It often sounds a bit formal or objective.

点数 also means score/points, but it is very common in everyday contexts too, especially for test scores.

A rough comparison:

• 得点 = score obtained, often in games, tests, competitions, systems
• 点数 = points/score, often very common in ordinary speech

In many contexts they overlap, but 得点を確認する sounds perfectly natural for check the score.

No, it is in the plain style.

The sentence ends with 確認する, not 確認します, so it is not polite speech.

Plain form does not automatically mean rude. It is commonly used in:

• dictionary entries
• manuals
• written explanations
• casual speech
• neutral statements

A polite version would be:

私たちは拡張版を選び、得点を確認します。

That sounds more polite and appropriate for formal conversation or respectful explanation.

Formally, the final verb is in the non-past form: 確認する.

In Japanese, non-past can cover several meanings depending on context, such as:

• present habitual: we choose ... and check ...
• future: we will choose ... and check ...
• general procedure: we choose ... and check ...
• instruction/manual style: choose ... and check ...

So you should not force it into only one English tense without context.

Yes, but it sounds more like written or structured language than casual conversation.

A native speaker might use it in:

• a manual
• a game explanation
• a formal description of a process
• a report
• a narration of rules or actions

In casual speech, they might be more likely to say something like:

• 拡張版を選んで、得点を確認する。
• 拡張版を選んで、スコアを確認する。

So the original sentence is grammatical and natural, but it has a somewhat formal, explanatory tone.