hòuxuǎnrén zhèngzài zuò zìwǒjièshào.

正在 marks an action that is in progress right now. It is similar to be doing in English.

So in this sentence, 正在做自我介绍 means the candidate is giving / is making a self-introduction right now.

A few related forms:

• 在
  • verb
• 正在
  • verb
• 正
  • verb

All can show an ongoing action, but 正在 is a very clear and common way to emphasize that something is happening at the moment.

In Mandarin, words that mark time, aspect, or manner usually come before the main verb.

So the pattern is:

subject + 正在 + verb + object

In this sentence:

• 候选人 = subject
• 正在 = ongoing-action marker
• 做 = verb
• 自我介绍 = object

So:

候选人 正在 做 自我介绍。

This word order is very normal in Chinese.

Yes. That is also correct.

These are all natural:

• 候选人正在做自我介绍。
• 候选人在做自我介绍。
• 候选人正做自我介绍。

The differences are small:

• 正在 sounds a bit more explicit about right now
• 在 is very common and slightly simpler
• 正 is shorter and also common in speech and writing

Because 自我介绍 often functions like a noun phrase meaning a self-introduction, and 做 can mean to do / to give / to make in many activity expressions.

So 做自我介绍 literally looks like:

do a self-introduction

This is a very common Chinese expression.

English and Chinese do not always choose the same verb.
English says give a self-introduction or introduce oneself, but Chinese often says 做自我介绍.

It can behave like either, depending on context.

In 做自我介绍, it acts like a noun phrase:

• 做 = do/give
• 自我介绍 = a self-introduction

But Chinese also allows 自我介绍 to act more verbally in some contexts.

For example:

• 请先自我介绍一下。 = Please introduce yourself first.

So it is useful to think of it as a flexible expression. In your sentence, though, it is easiest to understand it as the object of 做.

Yes, absolutely.

候选人正在介绍自己。 also means the candidate is introducing himself or herself.

The difference is mostly in style:

• 做自我介绍 is a very common set expression for giving a self-introduction, especially in formal situations like interviews, meetings, and classes.
• 介绍自己 is also correct, but it feels a little more directly verbal: introduce oneself.

In an interview or formal presentation, 做自我介绍 is especially common.

候选人 means candidate.

It can be used for different kinds of candidates, such as:

• a job candidate
• an election candidate
• a competition finalist/candidate

In your sentence, the exact kind of candidate depends on context. If this is about a job interview, then 候选人 means the applicant / candidate.

Breakdown:

• 候选 = to be a candidate / to stand as a candidate
• 人 = person

So together: candidate person, or simply candidate.

It could be either.

Mandarin usually does not mark gender in spoken third-person reference the way English often does.
So 候选人正在做自我介绍 just means:

• the candidate is introducing himself
• the candidate is introducing herself
• the candidate is giving a self-introduction

The sentence itself does not tell you the gender.

Yes, you can.

候选人正在做自我介绍呢。

Adding 呢 can make the sentence sound a bit more like:

• the action is ongoing
• the speaker is describing what is happening right now
• the tone is slightly more conversational

Without 呢, the sentence is still completely correct and natural.

In modern Mandarin, 做自我介绍 is the normal choice.

You may occasionally see 作自我介绍, especially in more formal or older-style writing, because 做 and 作 overlap in some usages. But for everyday modern Chinese, 做 is the safer and more common option here.

So learners should usually say:

做自我介绍

not

作自我介绍

It is pronounced:

hòuxuǎnrén

Tone pattern:

• 候 = fourth tone, hòu
• 选 = third tone, xuǎn
• 人 = second tone, rén

A rough guide:

• hòu sounds like a sharp falling tone
• xuǎn dips down and rises
• rén rises

Try saying it slowly first:

hòu — xuǎn — rén

Then more smoothly:

hòuxuǎnrén

Yes, if the subject is already clear from context.

Chinese often omits subjects when they are understood. For example, if everyone is watching one person speak, you can simply say:

正在做自我介绍。

But if you are introducing the situation from scratch, including 候选人 makes the sentence clearer.

You can add the listener after the verb phrase, often with 给:

候选人正在给大家做自我介绍。

Breakdown:

• 候选人 = the candidate
• 正在 = is currently
• 给大家 = to everyone
• 做自我介绍 = give a self-introduction

This is a very natural extension of the original sentence.