Which of the following is NOT a possible isomer of hexane?

2-ethyl pentane is not a possible isomer of hexane. Hexane (C6H14) has several isomers, including n-hexane, 2-methylpentane, 3-methyl pentane, 2,2-dimethyl butane, and 2,3-dimethyl butane. However, 2-ethyl pentane is not a valid isomer because it implies a seven-carbon chain, which does not align with the molecular formula of hexane (C6H14).