Which one has the highest boiling point?

Excretory organs in $Taenia$ are

Which of the following metals is the most reactive?

The $\Delta H^o$ of combustion of $C_4H_{10(g)}$ is $-2650 \ kJ \ mol^{-1}$. The amount of heat evolved at constant pressure that can be obtained by burning $5.8 \ kg$ of $C_4H_{10}$ is approximately:

If the vector $a = 2\hat{i} + 3\hat{j} + 6\hat{k}$ and $b$ are collinear and $|b| = 21$,then $b$ is equal to:

An electron moving with a speed $u$ along the positive $x-$ axis at $y = 0$ enters a region of uniform magnetic field $\vec{B} = -B_0\hat{k}$ which exists to the right of the $y-$ axis. The electron exits from the region after some time with the speed $v$ at coordinate $y$. Then: