The species having tetrahedral shape is

Stimulation of a muscle fiber by a motor neuron occurs at:

Based on the compounds of group $15$ elements, the correct statement($s$) is (are)

$(A)$ $Bi _2 O _5$ is more basic than $N _2 O _5$

$(B)$ $NF _3$ is more covalent than $BiF _3$

$(C)$ $PH _3$ boils at lower temperature than $NH _3$

$(D)$ The $N - N$ single bond is stronger than the $P - P$ single bond

Statement $S$: Presence of a rigid cell wall and nucleoprotein as genetic material.
Statement $R$: Examples include $Euglena$,$Dinoflagellates$,$Amoeba$,and $Paramecium$.

The maximum value of $xy$ subject to $x+y=7$ is

$A$ uniform rod of mass $M$ and length $L$ is placed on a smooth horizontal surface. $A$ horizontal force $F$ is applied at one end of the rod perpendicular to its length. The acceleration of the centre of mass of the rod is: