Which of the following has the lowest heat of hydrogenation per mole?

The number of roots of the equation $(81)^{\sin ^2 x} + (81)^{\cos ^2 x} = 30$ in the interval $[0, \pi]$ is equal to

$\int\left(\sqrt{\frac{a+x}{a-x}}+\sqrt{\frac{a-x}{a+x}}\right) d x$ is equal to

$y=e^{a \sin ^{-1} x} \Rightarrow (1-x^2) y_{n+2}-(2 n+1) x y_{n+1}$ is equal to

$A$ body of mass $2 \, kg$ moving with a velocity of $3 \, m/s$ collides head-on with a body of mass $1 \, kg$ moving in the opposite direction with a velocity of $4 \, m/s$. After the collision,the two bodies stick together and move with a common velocity. What is the common velocity in $m/s$?

Diborane reacts with ammonia under different conditions to give a variety of products. Which one among the following is not formed in these reactions?