Answer: Option B. -> 5, 5-Bis(1,1-dimethylpropyl)-2-methyldecane
:
B
Decide the parent chain and give the numbering so that more substituted substituent will get the least number.

parent chain
10 carbons $\Rightarrow$ word root $\Rightarrow$ dec
single bond $\Rightarrow$ suffix $\Rightarrow$ ane
substituents at $C_{5}and{C}_2$
Now,

There is one more same substituent on $C_5$
Therefore,
5,5-Bis-(1,1-dimethyl propyl)
Bis$\Rightarrow$ Because two same substituents are there, and a methyl group at $C_2\Rightarrow$ 2-methyl
Therefore,
5,5-Bis-(1,1-dimethylpropyl)-2-methyldecane

Answer: Option B. -> 3-Penten-1-yne
:
B
$\stackrel{1}{\underset{5}{C{H}_3}}-\stackrel{2}{\underset{4}{CH}}=\stackrel{3}{\underset{3}{CH}}-\stackrel{4}{\underset{2}{C}}\equiv \stackrel{5}{\underset{1}{CH}}$
From lowest sum rule, we will select $1,3$ and not $2,4$
Five carbons$\Rightarrow$ word root = pent
3-Penten-1-yne

Answer: Option B. -> Pent-1-en-4-yne
:
B
While naming, the double bond gets a lower number than the triple bond.
$\underset{1}{C}{H}_2=\underset{2}{C}H-\underset{3}{C}{H}_2-\underset{4}{C}\equiv \underset{5}{C}H$
Wort root = pent
Pent-1-en-4-yne
Not 4-Penten-1-yne
Because, if there is a choice in numbering, the double bond is always given preferenceover the triplebond.

Answer: Option C. -> 1-Ethyl-2-Methylcyclohexane
:
C
The numbering is according to the lowest of locants, which gives us two options.

In this case, numbering happens according to alphabetical order. So ethyl group will have thelower number.

word root = hex
primary prefix = cyclo
secondary prefix = 1-Ethyl-2-methyl
primary suffix = ane
IUPAC name is
(c)1-Ethyl-2-methylcyclohexane

Answer: Option B. -> 3-Ethyl-2,3-dimethylpentane
:
B
Decide parent chain.
Numbering so that more substitutedsubstituent will get the lowest number.

Five carbons $\Rightarrow$ word root = pent
single bonds = ane(suffix)
$\to$ substituent at $C_{2}and{C}_3$
$\Rightarrow$ 3-ethyl-2, 3-dimethylpentane(alphabetically)
Therefore,
(b)3-Ethyl-2,3-dimethylpentane

Answer: Option C. -> 3-(Chloromethyl)-3-methylpentane
:
C

Word root = pent
Primary suffix = ane
Lowest locant set = 3,3
Secondary prefixes = 3-(chloromethyl)-3-methyl
IUPAC name is 3-(chloromethyl)-3-methylpentane

Answer: Option D. -> 2-Chloro-2-methylpropane
:
D
The given compound tertiary butyl chloride is

It is numbered as shown.
The longest chain clearly includes 3 carbon atoms
$\Rightarrow$ root word = prop
primary suffix = ane
Secondary prefix = 2-chloro-2-methyl
Hence the name (systematic IUPAC) of given compound is:
(d)2-Chloro-2-methylpropane

Answer: Option A. -> 6-Ethyl-3,3-dimethylcyclohex-1-ene
:
A
In this compound, the parent chain is the one containing cycliccarbon.
Now, we number in the following way.

Because more substituted will get the lower number.
$\to$ethyl group at $C_5$
$\to$Two methyl group at $C_3$
Therefore, it will be
6-Ethyl-3-3-Dimethylcyclohex-1-ene
not
3,3-Dimethyl-6-ethylcyclohex-1-ene
Because we use alphabetical order and Di- is not considered for the alphabetical order.

Answer: Option A. -> 3-(Formylmethyl)hexanal
:
A
The given compound is:

Here we include as many -CHO groups as possible in the longest chain.Thus it is numbered as above (to give lowest possible number to the substituents -$C{H}_2-CHO$).This group is namedformylmethyl.
6 carbons = hex.
Since there are no carbon - carbon multiple bonds, primary suffix = ane; secondary suffix = dial.
Hence the IUPAC name is
(a) 3 -(Formylmethyl)hexanal
Note the parentheses indicating substituted substituent.
The compound could also be named 3-propylpentanedial

Answer: Option A. -> 3-Ethyl-4,4-dimethylheptane
:
A
First, check the parent chain.
Now, give numbers such that the more substituted substituent will get the lowest number.

Parent chain
7 carbon $\Rightarrow$ hept (word root)
Single bonds $\Rightarrow$ ane (suffix
$\to$ substituent at $C_{3}and{C}_4$ 3-ethyl-4,4-dimethyl(alphabetically)
Therefore, 3-Ethyl-4,4-dimethylheptane