Select the number from among the given options that can replace the question mark (?) in the following series.
48, ?, 12, 6, 3, 1.5

Let's analyze the pattern by moving from right to left or left to right:
3÷2=1.5

6÷2=3

12÷2=6

The pattern is clearly dividing by 2 at each successive term.
Following this rule from the beginning:

First term = 48

Second term (?) = 48÷2=24

Third term = 24÷2=12 (which matches the given series)

Thus, the missing number is 24.