A parasite which becomes saprophytic in the absence of host is called
A) Obligate parasite
B) Facultative parasite
C) Obligate saprophyte
D) Facultative saprophyte

Hint: Parasites are the organisms that live on or in a host organism and get its food from the host. Parasites can cause diseases in humans. Examples- stomach and gut worms, skin mites, hair and body lice, etc.

Complete Answer:
A) Obligate Parasites: Obligate parasites are also called the holoparasites.
- These parasites entirely depend upon the host for survival.
- These organisms cannot complete their life cycle without a suitable host.
 Example – lice, ear mites, etc.

B) Facultative Parasites: Facultative parasites are the organisms that can live freely and also can become parasitic on certain conditions.
- They become saprophytic in the absence of a host.
Examples- Mycobacterium tuberculosis.

C) Obligate saprophyte: Obligate saprophytes are the organisms that completely depend upon the dead matter for their survival.
- They cannot infect living plants and animals.
Examples – Rhizopus.

D) Facultative Saprophytes:
- These are the organisms that usually live parasitically, but they can become a saprophytic in the absence of a host.
 Example – Smut fungi.

So, as we see in the above discussion, a parasite which becomes saprophytic in the absence of a host is called a Facultative parasite.

Hence, option B will be the right option.

Note: Facultative parasites can live freely as a saprophyte in the absence of any host and also it becomes parasitic under certain conditions. They do not completely depend on the host.