Which of the statements is/are true for subtractive hybridization?

a. This technique is used to extract the mRNA transcripts that are expressed at lower levels.

b. The subtracted specific mRNA is reverse transcribed to cDNA and used to screen cDNA libraries.

c. The original mRNA from the subtractor cells remain intact in the solution and also get hybridized to cDNA

d. The unbound mRNA is isolated as the Complementary mRNA–cDNA molecules that are common to both cell types get hybridized.