Hey sorry for the late response but:
Answer:
I think its -C : e and f r paraller cause of alternative exterior angles ...
Explanation:
I feel C is right as :
Option a - The lines a and b's alternative exterior angles r not congruent(as not given)
Option b- there is no such rule like tht
Option c- Yes as the alternative exterior angles r congruent
Option d- No as there is no such rule and its not even true.
iI hope im right ..!!
(Pls tell me if im right or wrong)