Which of the following have $3C-2e^-$ bond?
$I.$ $Al_2Cl_6$
$II.$ $B_2H_6$
$III.$ $Fe_2Cl_6$
$IV.$ $Si_2H_6$

An inverted bell lying at the bottom of a lake $47.6 \, m$ deep has $50 \, cm^3$ of air trapped in it. The bell is brought to the surface of the lake. The volume of the trapped air will be ......... $cm^3$ (atmospheric pressure $= 70 \, cm$ of $Hg$ and density of $Hg = 13.6 \, g/cm^3$).

In which of the following plants can hybrid embryos be obtained?

Assertion : Replication and transcription occur in the nucleus but translation takes place in the cytoplasm.
Reason : $mRNA$ is transferred from the nucleus into the cytoplasm where ribosomes and amino acids are available for protein synthesis.

The time period of a particle in simple harmonic motion is $8 \ s$. At $t=0$,it is at the mean position. The ratio of the distances travelled by it in the first and second seconds is

$A$ transformer works on the principle of