a real DNA molecule consists of THOUSANDS of these pairs of nucleotides. What is the pairing arrangement of nitrogen bases

The correct answer is - Cytosine pairs with guanine and thymine pairs with adenine.

Explanation:

In a real DNA or B-DNA the interaction or arrangement of the nitrogen bases are defined and almost remain the same. The bond between the nitrogen bases is hydrogen bonds.

The hydrogen bond between the purine and pyrimidines  (types of nitrogen bases) are as follows:

Adenine always pairs with Thymine and Guanine always pairs with Cytosine in a real DNA molecule.

if your own plato the answer is b. the fern transitioned from sporophyte generation to gametophyte generation.