In compound $X$,all the bond angles are exactly ${109^o}28'$,$X$ is

$A$ vertical pole subtends an angle $\tan ^{-1}\left(\frac{1}{2}\right)$ at a point $P$ on the ground. If the angles subtended by the upper half and the lower half of the pole at $P$ are respectively $\alpha$ and $\beta$,then $(\tan \alpha, \tan \beta)$ is equal to

The magnetic flux through a stationary loop with resistance $R$ varies during an interval of time $T$ as $\phi = a t(T - t)$. The heat generated during this time,neglecting the inductance of the loop,will be:

The kind of tissue that forms the supportive structure in the pinna is also found in

From the figure describing the photoelectric effect,we may infer correctly that:

Which of the following is a pair of functional isomers?