the DNA strand given and complementary strand is as follows 5'–AAACTGT–3' 3' -TTTGACA- 5' There are 4 types of bases, Adenine, thymine, cytosine and guanine bases pair with the complementary base. A pairs with T through 2 hydrogen bonds G pairs with C through 3 hydrogen bonds when we draw the 2 strands vertically with the correct number of hydrogen bonds. DNA strand | complementary strand A = T A = T A = T C ≡ G T = A G ≡ C T = A 5 A-T bonds and 2 G-C bonds 2 H bonds for A-T and 3 H bonds for G-C Therefore total number of hydrogen bonds = (5*2) + (2*3) = 16