Final answer:
The stretching frequency of a C-H bond is highest in an alkyne.
Step-by-step explanation:
The stretching frequency of a C-H bond in an infrared (IR) spectrum is influenced by the type of carbon-hydrogen bond and the surrounding functional groups. In general, alkynes have the highest stretching frequency for a C-H bond, followed by alkenes, while alkanes have the lowest stretching frequency.
Therefore, the correct answer is C) Alkyne, as it has a C-H stretch that occurs at the highest stretching frequency.