It's more likely that (3) should be labeled "nucleotide". The accompanying image shows four possible molecules that resemble nucleotides.
Your answer for (2) is correct, since the arrows point to the dotted line indicating the interaction between base pairs on the double helix.
(1) seems to be pointing to the actual nucleotide that should pair up with guanine (notice the "G" printed on the nucleotide on the left), so I would say this should be cytosine.
