In the question given below, a part of the sentence is in bold and italicised. Below are given alternatives to the bold and italicised part which may improve the sentence. Choose the correct alternative. In case no improvement is needed, choose option 'D' as the answer.
Why the dinosaurs died out is not known.
A.
it is not known
B.
the reason is not known
C.
that is not known
D.
No improvement
Correct answer is D
No explanation has been provided for this answer.
