Which of the Following Is a Reason That Expressed Sequence

Which of the following is a reason that expressed sequence tags (ESTs) aid the identification of DNA that encodes proteins?

A) ESTs are amino acid sequences that can be used to predict the DNA sequence used in cellular gene expression.
B) ESTs are short DNA sequences conserved among all protein coding regions that can be scanned for by computer software.
C) ESTs are cDNA sequences and since cDNA synthesis uses an mRNA template ESTs identify protein coding genes.
D) ESTs are complementary to DNA promoter sequences and can act as coding region-specific primers.