Ideally the answer should be $20$ ns as it is the time to transfer a block from $L2$ to $L1$ and this time only is asked in question. But there is confusion regarding access time of $L2$ as this means the time to read data from $L2$ till CPU but here we need the time till $L1$ only. So, I assume the following is what is meant by the question.
A block is transferred from $L2$ to $L1$. And $L1$ block size being $4$ words (since $L1$ is requesting we need to consider $L1$ block size and not $L2$ block size) and data width being $4$ bytes, it requires one $L2$ access (for read) and one $L1$ access (for store). So, time $= 20+2 = 22$ ns.
Correct Answer: $C$