tuukinyouzitensya wo erabu.

It is read:

• 通勤用自転車 = つうきんようじてんしゃ
• を = を pronounced o
• 選ぶ = えらぶ

So the whole sentence is:

つうきんようじてんしゃ を えらぶ

A quick breakdown:

• 通勤 = commuting to work
• 用 = for use
• 自転車 = bicycle
• 選ぶ = to choose

用 in this kind of compound means for, for use in, or intended for.

So:

• 通勤用 = for commuting to work
• 家庭用 = for home use
• 業務用 = for business/professional use

In this sentence, 通勤用自転車 means a bicycle for commuting to work.

Because 通勤用自転車 is a noun compound.

Japanese often stacks nouns together to make compact expressions, especially in labels, product names, headlines, and concise writing.

So these are both possible:

• 通勤用自転車 = compact, compound style
• 通勤用の自転車 = more expanded, explanatory style

Both are natural. The version without の feels tighter and more like a category name or heading.

を marks the direct object of the verb.

Here:

• 通勤用自転車 = the thing being chosen
• 選ぶ = to choose

So the structure is:

[thing chosen] を [choose]

That is why 通勤用自転車 takes を.

選ぶ is the plain dictionary form of the verb.

In Japanese, this form can be used for:

• plain statements
• titles
• headings
• captions
• instructions in a concise style
• descriptions of actions in a neutral way

Depending on context, it can mean something like:

• choose
• chooses
• will choose
• to choose in a label-like sense

If you wanted a polite sentence, you could say:

• 通勤用自転車を選びます。

Japanese often leaves out the subject when it is already understood from context.

So 通勤用自転車を選ぶ。 could mean:

• I choose a commuter bicycle
• You choose a commuter bicycle
• We choose a commuter bicycle
• or simply Choose a commuter bicycle in a heading/instruction-like context

This is very normal in Japanese. Subjects are often omitted if they are obvious.

It can be either, depending on context.

By itself, 通勤用自転車を選ぶ。 often feels like:

• a heading
• a short description
• a step in a guide
• a casual plain-style sentence

For example, in an article, it could be a section title meaning something like Choosing a bicycle for commuting.

In everyday conversation, a fuller sentence might be more common, such as:

• 通勤用自転車を選びます。
• 通勤用の自転車を選ぶ。
• 通勤用自転車を選びたい。

No. Japanese is normally written without spaces.

So the normal writing is:

通勤用自転車を選ぶ。

The spaced version:

通勤用自転車　を　選ぶ。

is usually just for learners, readability, or formatting.

Usually 通勤 specifically means commuting to work.

A useful contrast is:

• 通勤 = commuting to work
• 通学 = commuting to school

So 通勤用自転車 is specifically a bicycle for getting to work, not just any kind of travel bicycle.

Not necessarily in the sense of being one rigid standalone vocabulary item, but it is a very natural compound.

Japanese often creates long noun phrases by combining parts:

• 通勤
  • 用
    • 自転車

So even if you do not memorize the whole thing as one separate word, you can understand it by its parts.

This is a very useful skill in Japanese, because long compounds are common.

Yes, absolutely.

• 通勤用自転車を選ぶ
• 通勤用の自転車を選ぶ

Both are natural.

A rough nuance difference:

• 通勤用自転車 feels more compact and category-like
• 通勤用の自転車 feels a little more explanatory and like ordinary sentence phrasing

In many situations, either one would work.