24. In precursor mRNA splicing, U6 snRNA can pair with two snRNAs and the intron site. These two snRNAs and intron site are: (A) U1 and U2, 5' splicing site (B) U1 and U4, 3' splicing site (C) U2 and U4, 5' splicing site (D) U2 and U5, 3' splicing site