Final answer:
A. Sexual reproduction
Roundworms typically engage in sexual reproduction, with separate male and female individuals producing sperm and eggs respectively, leading to high egg laying rates and a lifecycle from egg to larva then to adult.
Step-by-step explanation:
Most roundworms participate in sexual reproduction. This reproductive method involves separate male and female individuals, where sperm produced by males fertilizes the eggs contained within females. Females of roundworm species are known to lay a striking number of eggs, which can sometimes reach up to 100,000 per day. These eggs then hatch into larvae, progressing into adult worms and thus continuing the reproductive cycle.