Which of the following is not a type of laser?

$N_2H_4$ and $H_2O_2$ show similarity in

Given below are two statements,one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A:$ Isotopes of hydrogen have almost same chemical properties,but difference in their rates of reaction.
Reason $R:$ Isotopes of hydrogen have different enthalpy of bond dissociation.
In the light of the above statements,choose the most appropriate answer from the options given below:

State whether the following statements are True or False:
$(1)$ The metal and non-metal elements of $d$-block react with hydrogen to give molecular hydrides.
$(2)$ At normal temperature,dihydrogen reacts violently with dioxygen.

Metals of groups $7$,$8$,and $9$ do not form metallic hydrides. This is termed as

Which of the following statement$(s)$ is/are correct:
$A$. $NaH$ is a non-volatile hydride
$B$. $MgH_2$ is a polymeric hydride
$C$. $NH_3$ is an electron-precise hydride
$D$. $H_2O$ is an electron-rich hydride