Make sentence: In this class, there are twice more girls than boys

[Nhatanh]

This dance/ twice/ girls/ boys/there.

a. In this class , there are twice more girls than boys.
b. In this class , girls are twice more than boys.
c. In this class , there are twice as many girls as boys.
d. In this class , there are twice as much girls as boys.

I choose A, but I don't know why. Can you explain to me?

Thank you very much.

[Mister Micawber]

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No; choose C.
.
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Native English teacher at Mister Micawber's