In the process of DNA replication, each of the single strands becomes a double strand as an enzyme connects the appropriate complementary base to the exposed base.

b. the carbon cycle ensures living things have a source of hydrogen

not necessarily. higher fitness requires the organism to be reproductive successful. for example, an organism at age 10 with 15 offspring is much more fit than an organism at age 15 with only 5 offspring.

a metamorphic rock would be formed.