MCQ
What comes next: 1, 3, 7, 15, 31, ?
Biology
A 63
B 61
C 65
D 55
Explanation

Each term is multiplied by 2 and then 1 is added: 1×2+1=3, 3×2+1=7, 7×2+1=15, 15×2+1=31, 31×2+1=63.