The molecule name is called “4-Isopropyl-2,6-dimethyloctane”
The word “octane” indicates that we have a total of 8 carbons in our main chain. Therefore we can eliminate option 1.
Option 2 contains a ring, but in the molecule name, we do not see the prefix “cyclo”, making option 2 incorrect.
Option 4 has two methyl groups, position 2 and 7. In the molecule name, the two methyl groups are on position 2 and 6, making option 4 an incorrect answer.
Therefore, the 3rd option is correct.
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