Question

4. Why is there controversy about whether or not a virus is alive?

Answer 1

Mostly because they are made up of living cells, but in the bigger picture they are not alive.

Answer 2

Mostly because it can reproduce inside the host cell but cannot show any sign of life outside the host cell .
As it also causes various kind of diseases to the human but also some virus is used to make vaccinations .So, it has became controversy about both living and non living thinks.