Task: Question Answering
Input (English): Background Paragraph: A) In a straight-chain molecule, all the carbon atoms are lined up in a row like cars of a train. The carbon atoms form the “backbone” of the molecule. B) In a branched-chain molecule, at least one of the carbon atoms branches off from the backbone. C) In a cyclic molecule, the chain of carbon atoms is joined at the two ends to form a ring. Each ring usually contains just five or six carbon atoms, but rings can join together to form larger molecules. A cyclic molecule generally has higher boiling and melting points than straight-chain and branched-chain molecules. 
Story: Mark works as a scientist for a molecular research institute. Today, he has three samples of molecule in front of him, sample A, sample B, and sample C. Sample A is a straight-chain molecule; sample B is a branched-chain molecule; and sample C is a cyclic molecule. Mark's job is to determine the characteristics of each sample. 
Question: In which sample carbon atoms would line up in a row, sample A or sample C?
Output (English): sample A.