6. For the oligoribonucleotide pACGUAC:
a. the nucleotide at the 3' end has a phosphate at its 3' hydroxyl.
b. the nucleotide at the 3' end is a purine.
c. the nucleotide at the 5' end has a 5' hydroxyl.
d. the nucleotide at the 5' end has a phosphate on its 5' hydroxyl.
e. the nucleotide at the 5' end is a pyrimidine.