Final answer:
Pinworms, correctly identified as option c), are classified with ascarids as roundworms, belonging to the larger group of parasites known as helminths.
Step-by-step explanation:
Ascarids and pinworms are classified into a large group of parasites known as roundworms. The correct answer to this question is c) Pinworms. Roundworms are also known as nematodes, which are unsegmented worms with a full digestive system, even when parasitic. Helminths are divided into two major groups: the roundworms (Nematoda) and the flatworms (Platyhelminthes).
The group Nematoda includes several important human parasites such as the Ascaris lumbricoides, which can cause a range of symptoms from mild to severe. The flatworms include cestodes (tapeworms) and trematodes (flukes), which are important parasitic flatworms affecting humans. Note that cestodes and trematodes are not grouped under roundworms but are classified separately as flatworms due to their distinct body shapes and biological characteristics.