The correct answer is a if you want to make a cDNA library it does not matter which tissue you isolate the mRNA from.
Explanation:
cDNA is also called complementary DNA is generated from mRNA molecule by the process called reverse transcription with the help of reverse transcriptase enzyme.
During the formation of cDNA library at first mRNA is being isolated from a cell but it does not matter from which cell the mRNA is isolated because cDNA library is not specific for any particular mRNA present in a cell.
In a library there are various types of books.A library is not specific for a single type of book by the same way cDNA library is not specific for a single type of mRNA.
