Negative with comparative (need help)

[IllahNazaruddin]

Hi friends,
Here I am studying for TOEFL test next week. It's a question I totally hard to understand. The question is:
(woman): Is Paula lazy, as usual, this semester?
(man): She's never tried harder
Narrator: What does the man mean?

a. Paula is always lazy
b. Paula didn't work very hard this semester
c. Paula mad strong efforts
d. Paula could have work harder

I think the best answer would be B. But the key answer is C. It made me confused.
Can anybody give me a help please? Thank you

Naza

[Kitosdad]

She's never tried harder.

She has done her very best, and worked long and hard.
_________________
Keep it simple ... Keep it interesting.

[IllahNazaruddin]

Thank you Kitosdad. but She's never tried harder, how she has done very best?
Thanks.

[Stefan_V]

It means that Paula has never tried harder in the past than she did in this semester - therefore she tried harder in this semester than she ever has done before.

[IllahNazaruddin]

I got the point now. Thank you so much Stefan.

Naza