In addition to a carbonyl stretch, which of the following molecules exhibits two characteristic stretches at 2700 and 2800 cm^-1?

A) (CH₃CH₂) ₂CO
B) CH₃CH₂CH₂CHO
C) CH₃CH₂CO₂CH₃
D) CH₃CH₂CH₂CO₂H
E) CH₃CH₂CH₂COCl

The characteristic stretches at 2700 and 2800 cm-1 correspond to the CH3 and CH2 stretches, respectively. This indicates the presence of both methyl and methylene groups in the molecule. The only molecule that fits this description is B, which has both CH3 and CH2 groups in its structure. The other molecules either do not have both types of groups or have other functional groups that would cause additional characteristic stretches.