What should come in place of (?)

15  21  39  77  143  (?)

A.  243

B.  240

C.  253

D.  245

E.  None of these

What should come in place of the  (?) in the following letter series?

3  6  12  24  48  96  ?


A. 182

B. 186

C. 192

D. 198

What should come in place of the  (?) in the following letter series?

AC EQ IK MO ?


A. PR

B. QS

C. QR

D. PS