Comparing the time T1 taken for a single instruction on a pipelined CPU with time T2 taken on a non-pipelined but identical CPU, we can say that
Here we are comparing the execution time of only a single instruction. Pipelining in no way improves the execution time of a single instruction (the time from its start to end). It increases the overall performance by splitting the execution to multiple pipeline stages so that the following instructions can use the finished stages of the previous instructions. But in doing so pipelining causes some problems also as given in the below link, which might slow some instructions. So, (B) is the answer.
http://archive.is/XPYL look here.
http://www.cs.wvu.edu/~jdm/classes/cs455/notes/tech/instrpipe.html not working
Try this http://archive.is/XPYL (Its saved page of that link)