You Want to Design a Set of PCR Primers to Specifically

You want to design a set of PCR primers to specifically amplify a portion of a gene from genomic DNA.Which of the following statements about this set of primers is TRUE?

A) One of the primers should contain sequences complementary to common repetitive sequences in the genome, to ensure that it will hybridize to the genomic DNA.
B) Each primer should span the junction of two adjacent exons and leave out intron sequences, to ensure that a portion of the coding portion of the gene is amplified and not noncoding regulatory sequence.
C) If the primers include sequence from both an exon and the adjacent intron, this will help ensure that the amplified product is made from genomic DNA and not any contaminating mRNA.
D) The primers should use "U"s instead of "T"s to ensure that the coding portion of the gene is amplified.