Viruses
Reverse transcriptase is a useful enzyme to have when

there are no host cells present
an RNA virus converts its RNA to DNA
nutrients are scarce
spikes are forming in the new virus

ANSWER DOWNLOAD EXAMIANS APP

Viruses
The oncogene theory refers to

how chemicals inactivate viruses when applied
how viruses replicate in host cells
none of these
how viruses transform normal cells into tumor cells

ANSWER DOWNLOAD EXAMIANS APP