There is more to DNA than cytochrome c. This is just one protein.
b) cytosine pairs with guanine in both. literally in dna replication,
<em>adenine goes with thymine</em>
<em>thymine goes with adenine</em>
<em>guanine goes with cytosine</em>
<em>cytosine goes with guanine</em>
hope this helps mina! :) <3
Those are both examples of ecological services!