The Virus is called obligate parasites because:
a. The Virus must carry out their reproduction by parasitizing a host cell
b. They cannot multiply outside a living cell
c. They can only replicate inside a specific host
d. All of the above

Answer Verified Verified
Hint: When we are talking about a parasitic organism, we can say that it cannot finish its life cycle in deprivation to take advantage of an appropriate host known as an obligate parasite or holoparasite. Thus, we can conclude that if an obligate parasite cannot attain a suitable host, it will fail to replicate itself. They cannot do anything further without the help of a living organism

Complete answer:
- As we know, a Virus can be treated as a nucleoprotein entity since it is capable of using the synthetic machinery of an existing cell of other organisms for its multiplication. Besides, the other living cells does not involve the growth and the division of the Virus.

- The great scientist Pasteur was the one who coined the term virus before its systematic discovery. We can tell that within a non-living culture medium, virus cells cannot grow. For the sake of its metabolism and multiplication, it requires living cells essentially.

- Many can tell that Virus is known to be an obligate parasite as it is a sluggish exterior to the host cell. A virion is a name given to an inert virus. Since Biosynthetic machinery is absent, there is no system to release energy for it, thus, it results in no growth of the Virus. The Virus does not divide nor reproduce like unusual creatures without host gear.

- As we know, the virus cells multiply by the autonomous establishment of its parts utilizing host machinery and then assemble its parts to make virus subdivisions. In conclusion, we can tell that the virus deficiencies prickliness and motility. It entails a path for transmission from one host to another.

Hence, The correct answer is option (D).

Note: We know the organisms; viruses are joining a link amid the living and non-living organism. We can say that they are powerless to achieve life procedures external to the living cells of an organism. Outside the living cells, the viruses perform as unassuming substances. Thus, viruses are called an obligate intracellular parasite.