Question

1. which of these is a characteristic of viruses?

they invade hosts and reproduce within them.
they grow on surfaces containing nutrients.
they produce proteins and survive independently.
they form symbiotic relationships with hosts.

Explanation:

Viruses are non - cellular entities. They cannot grow on nutrient - containing surfaces like bacteria (which are cellular and can grow on such surfaces). They cannot produce proteins and survive independently as they lack the necessary cellular machinery. Symbiotic relationships involve a mutually beneficial or at least non - harmful co - existence. Viruses are obligate parasites. They invade host cells (using receptors on the host cell surface to attach) and then use the host cell's machinery (such as ribosomes for protein synthesis, nucleotides for nucleic acid synthesis etc.) to reproduce.

Answer:

They invade hosts and reproduce within them.