What is obtained by the reaction of $HCOOH$ with concentrated $H_2SO_4$?

How do ortho and para hydrogen differ from each other?

$NaH$ is an example of:

Hydrogen accepts an electron to form an inert gas configuration. In this property,it resembles:

Which of the following is not a type of laser?

Hydrogen has three isotopes $(A)$,$(B)$ and $(C)$. If the number of neutron$(s)$ in $(A)$,$(B)$ and $(C)$ respectively,are $(x)$,$(y)$ and $(z)$,the sum of $(x)$,$(y)$ and $(z)$ is: