@gottfriedweiser4860

21

@vbmaxg6575

c) 21 seems okay.
     2 + 3 = 5.
     3 + 5 = 8.
     5 + 8 = 13.
     8 + 13 = 21.

@eza1039

8+13=21

@waynethompson5956

C 21.

@a.v.akshethadevy1649

19