Final answer:
The final answer to the question about cDNA libraries is (D) I, II and III, as all statements are true, with cDNA libraries reflecting the expressed genes in a cell and lacking introns.
Step-by-step explanation:
The correct answer to the question regarding cDNA libraries is (D) I, II and III, meaning that all three statements are true. cDNA libraries are created from mRNA, and thus, lack introns due to the mRNA's prior processing through alternative splicing. These libraries reflect the transcriptome or the subset of genes that are being expressed in a particular cell or cell type at a particular time, which can indeed vary based on the cell from which the RNA was obtained.
Therefore, cDNA libraries can also be referred to as Expression Libraries, as they can isolate and sequence DNA that encodes for proteins being expressed at the moment of mRNA extraction.