The strands in a double helix of dna are:
a. wound around each other with 10 base pairs per turn.
b. held together via hydrogen bonds.
c. complementary.
d. antiparallel.
e. all of these choices are correct.

option E) All of these choices are correct.

Explanation:

The strands in a double helix of DNA are:

- wound around each other with 10 base pairs per turn.

According to Watson-crick model, DNA molecule consists of TWO chains wound around each other at right angles to form a DOUBLE HELIX with 10base pairs per turn.

- held together via hydrogen bonds.

Hydrogen bonds hold together the pairs of bases, as Adenine pairs with thymine by 2 hydrogen bonds, and cytosine pairs with guanine by 3 hydrogen bonds.

- complementary.

The double helix is specific as pairing ALWAYS occurs between Adenine and thymine, and between Cytosine and Guanine. thus it is complementary.

- antiparallel.

DNA strands DO NOT run in the same direction, thus they are antiparallel. i.e one strand runs in 5' - 3' direction, and the other run 3' - 5' direction, so one strand ascends while the other descends.

So, all of these choices are correct.

the answer is d (apex) good luck : ))