\textbf{210-} In naming alkanes, which carbon atoms of the main chain can be numbered from both ends of the chain?
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(1) 3, 2 — di methyl — 2 — pentene \qquad (2) 4, 2 — di methyl — 2 — hexene\\
(3) 4, 2 — di methyl — 2 — pentene \qquad (4) 5, 2 — di methyl — 3 — hexene
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