Which option shows the displayed formula for pentane?

• A. CH3-CH2-CH2-CH2-CH3
• B. CH3-CH2-CH2-CH2-CH2-CH3
• C. C5H12
• D. CH4

Answer: (A)

Pentane is a straight-chain alkane with five carbon atoms connected by single bonds. In a displayed (structural) formula, the chain is shown with the end carbons as CH3 and the internal carbons as CH2, reflecting the five-carbon backbone. The five-carbon sequence CH3-CH2-CH2-CH2-CH3 matches this, showing the five carbon atoms in a row with the correct types of carbon-hydrogen groups.

The other options don’t fit pentane: a six-carbon chain would be hexane, not pentane; a molecular formula (C5H12) doesn’t show how the atoms are connected; and methane has only one carbon.