Here are the answers for each part of your questions:
Part A: In a DNA double helix, an adenine of one strand always pairs with a(n) thymine of the complementary strand, and a guanine of one strand always pairs with a(n) cytosine of the complementary strand.
Part B: After DNA replication is completed, each new DNA double helix consists of one old DNA strand and one new DNA strand.
Part C: The first step in the replication of DNA is catalyzed by helicase.
Part D: The action of helicase creates replication forks and replication bubbles.
Part E: The new DNA strand complementary to the 3' to 5' strand is assembled in short segments because DNA polymerase can assemble DNA only in the 5' to 3' direction.
Part F: The synthesis of a new strand begins with the synthesis of a(n) RNA primer complementary to a preexisting DNA strand.
Part G: An old DNA strand is used as a template for the assembly of a new DNA strand.