C3H8 is propane, which is an alkane. Alkanes are a homologous series, meaning they share the same general formula and have similar chemical properties. The general formula for alkanes is CnH2n+2.

To find a compound in the same homologous series, we need to find another compound with the same general formula. Here's how to do it:

1. Identify the number of carbon atoms in C3H8: There are 3 carbon atoms.

2. Change the number of carbon atoms to find other members of the series:

* Increase the number of carbons: C4H10 (butane) is the next member of the series.

* Decrease the number of carbons: C2H6 (ethane) is the previous member of the series.

Therefore, butane (C4H10) and ethane (C2H6) are members of the same homologous series as propane (C3H8).