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 lack the machinery to reproduce on their own. So, they invade host cells (such as bacterial cells, animal cells, or plant cells). Once inside the host cell, they use the host's cellular machinery (like ribosomes for protein synthesis, nucleotides for nucleic acid synthesis etc.) to reproduce.
They do not grow on nutrient - containing surfaces like bacteria (which can be cultured on agar plates with nutrients). Viruses cannot survive independently as they need a host for their metabolic and reproductive processes. Also, they do not form symbiotic relationships (where both the virus and the host would benefit in a mutualistic symbiosis, or one benefits and the other is unharmed in commensalism) with hosts. Instead, they are generally parasitic (the virus benefits at the expense of the host).

Answer:

They invade hosts and reproduce within them.