Final answer:
A C-H bond absorbs at higher frequencies compared to a C-D bond because hydrogen is lighter than deuterium, and according to the mass-spring model, a lighter mass vibrates at a higher frequency.
Step-by-step explanation:
When comparing which bond absorbs at higher frequencies, a C-H bond or a C-D bond (where D represents deuterium, an isotope of hydrogen), the answer is: A) the C-H bond.
This is because bond vibration frequencies depend on the masses of the atoms in the bond as well as the strength of the bond. Deuterium has a greater mass than hydrogen (approximately twice as heavy). As per the classic mass-spring model analogy in physics, a heavier mass on the same spring (representing the bond strength) will oscillate at a lower frequency. Thus, the C-H bond, being lighter, vibrates at a higher frequency and consequently absorbs infrared light at higher frequencies compared to the C-D bond.