The given binary number is 1011 to base 2
To convert it to base 10, he first step is to number the digits from the right and starting the numbering from zero. We have
1 0 1 1
0 1 2 3
By converting to base 10, it becomes
1 x 2^3 + 0 x 2^2 + 1 x 2^1 + 1 x 2^0
= 8 + 0 + 2 + 1
= 11
Option B sis correct