Read the following sentences and choose the ones belonging to the domain of complex sentences.
A. That Shankar is clever is certain.
B. I do not know whether the principal is in the office.
C. Rennie is not only kind but also devoted.
D. Can you tell me the reason why Mukti never smiles ?
Choose the correct answer from the options given below :

A

A, Band Conly

B

B, C and D only

C

A, C and D only

D

A, B and D only