The genetic material of a reovirus is:

Which scientist demonstrated that the extract of infected tobacco plants could cause infection in healthy plants?

What was the significant contribution of the scientist $W$. $M$. Stanley in $1935$ regarding viruses?

$T. O.$ Diener discovered a new infectious agent that was smaller than viruses and has the following characteristics:
$(i)$ It causes potato spindle tuber disease.
$(ii)$ It has free $RNA$.
$(iii)$ The molecular weight of $RNA$ is low.
Identify the infectious agent.

Which of the following are most suitable indicators of $SO_2$ pollution in the environment?

Identify the part labeled as $'D'$ in the given figure.