The elongation of the leading strand during DNA synthesis a. progresses away from the replication fork. b. occurs in the 3′→5′ direction. c. produces Okazaki fragments. d. depends on the action of DNA polymerase.

Verified step by step guidance

1. Step 1: Understand the process of DNA replication. DNA replication is a process that occurs in all living organisms and is the basis for biological inheritance. The process is initiated at specific locations in the genome, called 'origins'. Unwinding of DNA at the origin, and synthesis of new strands, forms a replication fork.
2. Step 2: Identify the leading strand. In DNA replication, the leading strand is the template strand of the DNA molecule that is being replicated in a 3' to 5' direction. The leading strand is synthesized continuously in the direction of the replication fork.
3. Step 3: Evaluate the options. Option a suggests that the elongation of the leading strand progresses away from the replication fork. This is incorrect because the leading strand is synthesized in the direction of the replication fork. Option b suggests that the elongation occurs in the 3' to 5' direction. This is incorrect because the leading strand is synthesized in the 5' to 3' direction. Option c suggests that the elongation produces Okazaki fragments. This is incorrect because Okazaki fragments are produced during the synthesis of the lagging strand, not the leading strand.
4. Step 4: Choose the correct answer. Option d suggests that the elongation of the leading strand depends on the action of DNA polymerase. This is correct. DNA polymerase is the enzyme that synthesizes the new DNA by adding nucleotides to the 3' end of a DNA strand.
5. Step 5: Confirm the answer. DNA polymerase is indeed responsible for the elongation of the leading strand during DNA synthesis, so the correct answer is option d.