Complete the series: 1, 3, 7, 15, 31, 63, _

by

A) 120
B) 124
C) 127 
D) 135

🧠 Explanation (Math):

Given: Series 1, 3, 7, 15, 31, 63, _
Step 1: Differences are 2, 4, 8, 16, 32 (= powers of 2)
Step 2: Next difference = 64
Step 3: Next term = 63 + 64 = 127
Final Answer: 127