Waar wachten de passagiers op?

Because wachten op is the normal Dutch combination for to wait for.

In this question, the object of the preposition is represented by waar, and the preposition op is left at the end:

• Waar wachten de passagiers op?

This is very common in Dutch. English does something similar in What are the passengers waiting for?, where for also ends up at the end.

So it helps to think of wachten op as a unit:

• wachten = to wait
• wachten op = to wait for

In Dutch, when you ask about a thing after a preposition, you usually use waar + preposition, not wat + preposition.

So:

• Waar ... op? = what ... for?
• literally something like where ... on?, but that literal breakdown is not how it functions

That is why Dutch says:

• Waar wachten de passagiers op?

and not normally:

• Wat wachten de passagiers op?

A useful rule:

• wie is used for people
• waar + preposition is used for things

For example:

• Waar denk je aan? = What are you thinking about?
• Waar kijk je naar? = What are you looking at?

Yes. Waarop wachten de passagiers? is grammatically correct.

Dutch often allows two versions:

• Waar wachten de passagiers op?
• Waarop wachten de passagiers?

The split version with the preposition at the end is usually more common and natural in everyday speech. The combined version waarop can sound a bit more formal or written, depending on context.

So as a learner, Waar wachten de passagiers op? is an excellent, natural choice.

Because this is a wh-question in Dutch.

Dutch main clauses follow the verb-second rule, and in a question with a question word, the finite verb usually comes right after the question word:

• Waar
  • wachten
    • de passagiers
      • op?

So:

• Waar = question word
• wachten = finite verb
• de passagiers = subject

This is normal Dutch word order in questions:

• Wanneer vertrekt de trein?
• Waarom lachen de kinderen?
• Waar wachten de passagiers op?

Because Dutch often uses the simple present where English uses the present continuous.

So Dutch:

• De passagiers wachten op de bus.

can mean:

• The passengers wait for the bus or
• The passengers are waiting for the bus

The exact meaning depends on context.

English strongly prefers are waiting for an action happening now, but Dutch does not need a separate continuous form here.

Yes, very much so.

Dutch wachten often goes together with op when you mean wait for someone or something.

Examples:

• Ik wacht op de trein.
• We wachten op onze vrienden.
• Zij wachten op toestemming.

So when learning wachten, it is smart to learn it as:

• wachten op iets/iemand = to wait for something/someone

That will help you avoid mistakes like using the wrong preposition.

De passagiers means the noun is:

• plural
• definite

So:

• passagier = passenger
• passagiers = passengers
• de passagiers = the passengers

In Dutch, plural nouns normally take de, not het.

Compare:

• de passagier = the passenger
• de passagiers = the passengers

A normal statement would be:

• De passagiers wachten op de trein.
• De passagiers wachten op hun bagage.

The basic word order in a statement is:

• subject + verb + rest

So:

• De passagiers = subject
• wachten = verb
• op ... = prepositional phrase

In the question, the thing being waited for is replaced by the question structure:

• Waar wachten de passagiers op?

No. If you are asking about a person, Dutch uses op wie.

So:

• Waar wachten de passagiers op? = asking about a thing
• Op wie wachten de passagiers? = asking about a person

This is an important difference:

• waar + preposition = thing
• preposition + wie = person

Examples:

• Waar denk je aan? = What are you thinking about?
• Aan wie denk je? = Whom are you thinking about?

Not exactly. It is related in meaning, but the pronunciation is Dutch.

A learner should especially notice:

• the g in passagiers is Dutch, not English
• the final -iers does not sound like English -ers

A rough English-friendly approximation is something like:

• pah-sah-KHEERS

But that is only approximate. The real Dutch pronunciation has a Dutch g/ch sound that English does not normally have.

So it is best to listen to native audio and repeat it rather than relying too much on spelling.