Who discovered viroids?

Haploid plants are obtained from which of the following?

The amplitude of a wave represented by the displacement equation $y = \frac{1}{\sqrt{a}} \sin \omega t \pm \frac{1}{\sqrt{b}} \cos \omega t$ will be

The maximum value of $\frac{\log x}{x}, 0 < x < \infty$ is

The $H-$ zone in the skeletal muscle fibre is due to:

Product $(A)$ is