$IUPAC$ name of the following compound $(P)$ is:

The $IUPAC$ name(s) of the following compound is(are):
$[A]$ $4-$methylchlorobenzene
$[B]$ $4-$chlorotoluene
$[C]$ $1-$chloro$-4-$methylbenzene
$[D]$ $1-$methyl$-4-$chlorobenzene

Structures and $IUPAC$ names of some hydrocarbons are given below. Explain why the names given in the parentheses are incorrect.
$(a)$ $CH_3-CH(CH_3)-CH_2-CH_2-CH(CH_3)-CH(CH_3)-CH_2-CH_3$
Name: $2,5,6-$Trimethyloctane [and not $3,4,7-$Trimethyloctane]
$(b)$ $CH_3-CH_2-CH(CH_2CH_3)-CH_2-CH(CH_3)-CH_2-CH_3$
Name: $3-$Ethyl$-5-$methylheptane [and not $5-$Ethyl$-3-$methylheptane]

The $IUPAC$ name of the compound having the formula $CH \equiv C-CH=CH_2$ is

The decreasing order of priority for the following functional groups in the $IUPAC$ Nomenclature is $-SO_3H$,$-CN$,$-COOH$,$-OH$,$-CHO$.

In the $IUPAC$ system, $PhCH_{2}CH_{2}CO_{2}H$ is named as