yes girish, when the answer screams rite upfront, the challenge loses its importance.
Anyways, here is my explanation to help u with the concept.
The error tested- Tense error.
A) there is nothing wrong with the sentence. The tense is correctly aligned.
B) had been- past perfect tense. a past perfect tense needs 2 events. the later event in the past is assigned past perfect tense and the former past event is assigned simple past. But in our question we do not have 2 events. you might say led- is a past event but my answer is NO. it is not. it just is an implication. It is not an event that has occured in the past. Moreover the statement evolved currently is wrong. Eliminated!
C) 'are' is used for present continous tense. 'are evolved' is wrong tense usage. Eliminated!
D)'who presently are now evolved' is wrong. are they evolving now? moreover the mistake in C also transcends in D.Eliminated!
E) the present participle 'evolving now into sharks' modifies recent fossils. The meaning is wrong. The fossils are not evolving into basking sharks. Hence Eliminated!
