Which alkanes follows after butane in the series?

The correct answer is pentane because it follows the systematic nomenclature of alkanes in organic chemistry, where the name reflects the number of carbon atoms in the longest continuous chain.

In this case, butane has four carbon atoms (C4), and by adding one more carbon atom, we get pentane, which consists of five carbon atoms (C5). The nomenclature of alkanes is based on the prefix indicating the number of carbon atoms, so after butane comes pentane.

Other choices, such as hexane, heptane, and ethane, represent longer or shorter chains of carbon atoms (six, seven, and two carbon atoms, respectively) and do not follow immediately after butane in the series. Thus, pentane is the appropriate alkane that comes next in the sequence after butane.