The correct option is C 16
A toss of one coin has 2 (i.e., 21) possible outcomes (H and T).
Simultanous toss of two coins has 4 (i.e., 22) possible outcomes (HH, TT, HT and TH).
Simultanous toss of three coins has 8 (i.e., 23) possible outcomes.
Similarly, simultanous toss of four coins has 24=16 possible outcomes.