Which one of the following is not a parasitic adaptation?
A. Development of adhesive organs
B. Loss of digestive organs
C. Loss of reproductive capacity
D. Loss of unnecessary sense organs

Hint: Parasitism is a mode of nutrition where one organism ‘parasitizes’ the other. The organism that parasitizes is called a parasite; the other organism is known as the host. In order to live in the host, the parasite undergoes a variety of morphological alterations.

Complete answer:
Parasites are organisms that live within another organism, the host. The parasites live within the host and draw nutrition from them. In this process, the host suffers some harm. The parasite, to live in the host organism has developed some structural, physiological modifications. Some of the modifications are listed below:
Development of adhesive organs: The parasites have developed adhesive organs that help them to get attached to the host tissues. These organs can be suckers, hooks or rostellum.
Loss of sense organs: The parasites generally live inside the host. Thus, parasites do not need to react to change in their environments as opposed to free living animals. Hence, parasites lack sense organs.
Loss of digestive organs: Parasites do not have digestive organs, instead they have developed sucking mechanisms to absorb nutrients from the host organism.
Reproductive adaptation: Parasites have well developed reproductive ability. This is due to the fact that in order to infect new hosts and avoid extinction, the parasites reproduce with great vigor. Generally, parasites are hermaphrodite animals, in which both male and female reproductive organs are present in an organism. This arrangement allows self-fertilization in the host body.
Defense against host immunity: Parasites evade the components of the host immunity system by producing antigenic variations, developing high resistance to host toxins and absorption of host antigens.
Therefore, to conclude parasitic adaptations are loss of sense organs, digestive organs and development of suckers. However, reproductive organs, instead of being lost, are very well developed.
Hence, option (c) is correct.

Note: Parasites are very small organisms that live within other living organisms Parasites are known to cause reduced general fitness of the host organism, simultaneously increasing its own fitness. . In order to survive in their hosts, parasites have developed some morphological and physiological features, and have undergone loss of some body features.