Answer : 1. "0.5"
Explanation :

Answer: A) 0.5 Explanation: In mathematics, a geometric progression, also known as a geometric sequence, is a sequence of numbers where each term after the first is found by multiplying the previous one by a fixed, non-zero number called the common ratio.   Herein the given sequence, 4, 2, 1, 0.5, 0.25, 0.125,... Common Ratio r = 2/4 = 1/2 = 0.5/1 = 0.25/0.5 = 0.125/0.25 == 0.5.