Answer
D. 7-methyl-3-octyne
Step-by-step explanation
In naming Alkynes, the following rules stand:
Rule 1: Find the longest carbon chain that includes both carbons of the triple bond.
Rule 2: Number the longest chain starting at the end closest to the triple bond. A 1-alkyne is referred to as a terminal alkyne and alkynes at any other position are called internal alkynes.
Rule 3: After numbering the longest chain with the lowest number assigned to the alkyne, label each of the substituents at its corresponding carbon. While writing out the name of the molecule, arrange the substituents in alphabetical order. If there are more than one of the same substituents use the prefixes di, tri, and tetra for two, three, and four substituents respectively. These prefixes are not taken into account in alphabetical order.
The give alkyne has 8 longest carbon chain that includes the carbons with the triple bond. Carbon number 3 has the triple bond and a methyl substituent is bonded to carbon number 7 as shown below:
8 carbon chain with triple bond on carbon 3 -the parent name will be 3-octyne.
A methyl substituent is on carbon 7. Hence the name of the alkyne will be: 7-methyl-3-octyne.