Why are the strands of DNA said to be complementary to each other? A) The sugar-phosphate chains are running in opposite directions. B) The sugar-phosphate chains of each strand are identical. C) Both strands can have any of four possible bases attached. D) All the bases of one strand are paired up with their complementary bases on the other strand.
D, you need to know that DNA strands are antiparallel to each other and because A and T go with each other and G and C go with each other (the two sets of complementary base pairs) strands of DNA are complementary.
