Which is correct, please?

[hoangkha]

Hi!
She is working as a dental assistant. What she does is....... people's teeth.

c. cleaning
d. to clean

[jmacdonald]

Neither. It should be "What she does is clean people's teeth."

[bhtr88]

Neither. It should be "What she does is clean people's teeth."

Hi jmacdonald! You really puzzled me. I was sure that gerund should be used in this kind of sentences. Could you please provide more details. What kind of grammatical construction is this?

[emsr2d2]

What she is doing is cleaning people's teeth. (That would really only work if you were talking about what she is actually physically doing at the same time as you are speaking.)

What she does is clean people's teeth. (A general description of her job.)

[alenjones23]

I think the correct one would be "She is working as a dental assistant. What she does is clean people's teeth."

[hoangkha]

Neither. It should be "What she does is clean people's teeth."

Thank you.
I'm sorry. The full sentence is
- He is working as dental assistant. What she does is... people's teeth
a. clean
b. cleans
c. cleaning
d. to clean

I have just found this.
According to PEU by Micheal Swan.
Expressions like All I did was, What I do is etc can be followed by an infinitive without to.
- All I did was (to) give him a little push.
- What a fire-door does is (to) delay the spread of a fire.

[Natalie1991]

Neither. It should be "What she does is clean people's teeth."

This is correct.

"What she does is clean people's teeth"