The correct answer is $\boxed{\text{B. }110}$.
The sequence is a list of binary numbers, where each number is formed by the previous number with one additional bit set to 1. For example, $11$ is formed by setting the rightmost bit of $10$ to 1, and $100$ is formed by setting the rightmost bit of $11$ to 1.
Option A, $101$, is not in the sequence because it does not follow the pattern of each number being formed by the previous number with one additional bit set to 1.
Option B, $110$, is in the sequence because it is formed by setting the rightmost bit of $10$ to 1.
Option C, $111$, is not in the sequence because it does not follow the pattern of each number being formed by the previous number with one additional bit set to 1.
Option D, None of these, is not correct because $110$ is in the sequence.