Which of the following is true for viruses?

Explanation

Viruses are unique infectious agents with certain defining features, and among the given statements, the correct one is that they multiply only in host cells. The claim that viruses occur only inside bacteria is incorrect, because although some viruses specifically infect bacteria (bacteriophages), many others infect plants, animals, fungi, and humans. The idea that they are made up of proteins only is also wrong, as all viruses contain genetic material in the form of either DNA or RNA in addition to a protein coat, and some also have a lipid envelope. Similarly, the statement that they behave as if they are plants is misleading, since viruses do not carry out plant-like functions such as photosynthesis. The only accurate description is that viruses multiply only inside host cells, as they are obligate intracellular parasites and depend entirely on the machinery of living cells to reproduce.