A learner makes a note: a large intestinal roundworm infects humans and may cause nutritional problems or intestinal blockage. The missing scientific idea is:

Correct Answer: B

Ascaris lumbricoides

Ascaris lumbricoides is a common human intestinal nematode. Eggs are usually transmitted through contaminated food, water, or soil. This MCQ belongs to the Nematoda topic in Animal Diversity-I and is written to test concept understanding rather than memorized wording.