The compound$(s)$ with $P - H$ bond$(s)$ is$(are)$
$(A) \ H _3 PO _4$ $(B) \ H _3 PO _3$ $(C) \ H _4 P _2 O _7$ $(D) \ H _3 PO _2$

In any $\triangle ABC$,the expression $\frac{(a+b+c)(b+c-a)(c+a-b)(a+b-c)}{4b^2c^2}$ is equal to:

Consider the following reaction,
$C_2H_5Cl + AgCN \xrightarrow{EtOH / H_2O} \underline{X} \text{ (major)}$
Which one of the following statements is true for $\underline{X}$?
$(I)$ It gives propionic acid on hydrolysis
$(II)$ It has an ester functional group
$(III)$ It has a nitrogen linked to ethyl carbon
$(IV)$ It has a cyanide group

Which one of the following ions exhibits the highest magnetic moment?

Which among the following has the highest melting point?

$A$ uniform metal rod of $2\,mm^2$ cross-section fixed between two walls is heated from $0\,^{\circ}C$ to $20\,^{\circ}C$. The coefficient of linear expansion of the rod is $12 \times 10^{-6}\,/^{\circ}C$. Its Young's modulus of elasticity is $10^{11}\,N/m^2$. The energy stored per unit volume of the rod will be ....... $J/m^3$.