Can you have a check on this?!

Here is the question.
Needs to put the sentence into the passive voice,

Someone stole his car.
My answer is:
His car was stolen by someone.

Is something wrong with it? Am sure of it it’s right.

But this site states there is something wrong in my answer.

Well try yourself and write down this answer in the answer text box under the question sentence and then click Check.

The answer which is accepted is ‘His car was stolen’.
I would guess that the argument is that ‘by someone’ is not needed as it is unlikely to have been stolen by anything other than a person. However, a computer spreadsheet can only possibly accept one answer, whereas a human being might accept alternatives.

Don’t look at the (accepted) answers below if you plan to do the exercise!

[color=blue][size=75]1 He usually buys the tickets.
The tickets are usually bought by him.
2 We booked the flights.
The flights were booked by us.
3 He opened the bottle easily.
The bottle was opened easily by him.
4 She cleans my shoes.
My shoes are cleaned by her.
5 They arrested the burglars.
The burglars were arrested by them.
6 He wrote the note.
The note was written by him.
7 They washed the car.
The car was washed by them.
8 She found the key.
The key was found by her.
9 He sold his coin collection.
His coin collection was sold by him.
10 We started a new system.
A new system was started by us.
11 Someone stole his car.
His car was stolen.
12 They used the towels.
The towels were used by them.
13 We turned on the TV.
The TV was turned on by us.
14 She served tea at 4.
Tea was served by her at 4.
15 The rain flooded the camp.
The camp was flooded by the rain.[/size]

Can you have a check on this?!

What is it you want to know about that webpage?
please :((

  1. He has lent her the umbrella.
    The umbrella …?

The umbrella has been lent to her by him.

The test says,‘Take the personal pronoun to start the sentence!’

Does the test ask for these passive forms below

  1. She was lent the umbrella.
  2. I was given a good advice.
  3. We were promised some money.
  4. He will be given a reward.
  5. I was told the whole story.
  6. She was sent the bill.
  7. We’ll be shown the way.
  8. She was paid a lot of money.
  9. It was written down correctly.
  10. He was kept awoken.
  11. I was sometimes taken to the station.
  12. I will be given his address.

If so, are my answers correct?