Through which cell of the embryo sac does the pollen tube enter the embryo sac?

The coefficient of apparent expansion of mercury in a glass vessel is $153 \times 10^{-6}/^{\circ}C$ and in a steel vessel is $144 \times 10^{-6}/^{\circ}C$. If $\alpha$ for steel is $12 \times 10^{-6}/^{\circ}C$,then $\alpha$ for glass is:

The incorrect stability order of $+3$ and $+1$ states of $13^{th}$ group elements (boron family) is

$A$ proton, a deuteron, and an $\alpha -$ particle enter a region of perpendicular magnetic field (to their velocities) with the same kinetic energy. If $r_p, r_d,$ and $r_{\alpha}$ are the radii of the circular paths of these particles, then:

Assertion : Comparative biochemistry provides a strong evidence in favour of common ancestry of living beings.
Reason : Genetic code is universal.

$CHO-(CHOH)_4-CH_2OH \xrightarrow{Br_2/H_2O} P$; $P$ is