Viruses behave as non-living entities because outside a host cell they:

The viruses responsible for causing polio and hydrophobia are

What was the contribution of the scientist $M. W. Beijerinck$ in $1898$ regarding the study of viruses?

Match the following columns.

Column $I$	Column $II$
$(A)$ $DJ$ Ivanowsky	$(i)$ Viroids
$(B)$ $MW$ Beijerinck	$(ii)$ Crystallised virus
$(C)$ $WM$ Stanley	$(iii)$ Contagium vivum fluidum
$(D)$ $TO$ Diener	$(iv)$ Mosaic disease of tobacco

Which of the following was discovered by the scientist $T$.$O$. Diener?

$A$ scientist $X$ demonstrated that the extract of infected plants of $Y$ could cause infection in healthy plants and called the fluid as "Contagium vivum fluidum". Identify $X$ and $Y$.