When orthoboric acid is heated,the residue left is ...

In a $\triangle ABC$,the expression $\frac{\cos C+\cos A}{c+a}+\frac{\cos B}{b}$ is equal to

Match the following columns:

Column-$I$	Column-$II$
$(A)$ Linnaeus	$(i)$ First to discover viruses
$(B)$ Ivanowsky	$(ii)$ First to discover lichens
$(C)$ Iyengar	$(iii)$ Father of Indian Bryology
$(D)$ Tulasne	$(iv)$ Father of Taxonomy
$(E)$ Shiv Ram Kashyap	$(v)$ Father of modern Phycology in India

The condition for diffraction is

Typhoid fever is caused by which of the following?

The temperature in $K$ at which $\Delta G = 0$ for a given reaction with $\Delta H = -20.5 \ kJ \ mol^{-1}$ and $\Delta S = -50.0 \ J \ K^{-1} \ mol^{-1}$ is: