In Ascaris, the period of incubation outside the human body is

The correct option is 15-30 days.

Ascaris lumbricoides is a giant intestinal roundworm parasite of humans. The eggs passed in the feces of an infected individual are not immediately infective. They must undergo a period of incubation and development in the external environment (soil) before they become infective to another host.
During this external incubation phase, the single-celled zygote within the egg shell undergoes cleavage and develops into a first-stage larva, which then molts to become the infective second-stage (rhabditiform) larva.
Under optimal environmental conditions (specifically, warm temperature, high humidity, and oxygen-rich moist soil), this incubation and maturation process outside the human body typically takes about 2 to 4 weeks, which corresponds to the 15-30 days range.