Which of the following compounds has 5 carbon atoms?

Pentane is the correct choice because its name is derived from the Greek word "penta," which means five. In organic chemistry, pentane is an alkane with the molecular formula C5H12. This compound consists of five carbon atoms connected in a straight chain, and it is commonly used as a standard in various chemical applications and as a solvent.

To further support this understanding, looking at the other compounds provides clarity. Hexane, for example, has six carbon atoms, indicated by "hex," which is the Greek prefix for six. Butane is comprised of four carbon atoms, as denoted by "but," the prefix for four. Lastly, octane contains eight carbon atoms; “oct” signifies eight. This systematic naming convention in organic chemistry aids in quickly identifying the number of carbon atoms in a compound based on its name.