[Grammar] saw them dance/dancing

[Oceanlike]

I am unsure of the answer to the following question:

- Jeannie saw a boy and a girl (dancing/danced/dance) to the tune of Grease.

Both dancing and dance seem right.
The reason for ‘dance’ being the right answer is the presence of the sense verb 'saw'. However, is ‘dancing’ acceptable also? If it is, please help me to understand the reason.

Thank you! :-D

 

[Matthew Wai]

I think the reason is that 'dancing' is a present participle modifying 'a boy and a girl', but I am not a teacher.

 

[Oceanlike]

I thought that after a sense verb 'saw' in this case, it should be followed by a base verb. Hence, the 'dance' is the correct answer.

However, the answer key suggests that 'dancing' is the correct answer. I don't understand the reason for 'dancing' being the correct answer after 'saw'.

Thank you!

 

[Matthew Wai]

Also compare:

I saw him write a cheque.
I saw him writing a thesis.

Not a teacher.