Final answer:
The bond with the greater polarity and strength absorbs at a higher frequency in an IR spectrum, with the carbonyl bond being an example of a strong absorber due to its polarity.
Step-by-step explanation:
The absorption frequency in an IR spectrum correlates to the bond strength and mass of the atoms involved. Higher frequency absorption, expressed as a higher wavenumber in cm¹, typically indicates a stronger bond or a bond between lighter atoms. For higher infrared absorption, the bond polarity plays a critical role as well. Given that a carbonyl bond is very polar, it absorbs strongly, suggesting that among the choices, the bond closest in nature to a carbonyl would absorb at a higher frequency.
Furthermore, considering bonds as springs, the 'bounce' frequency, or vibration frequency, will be higher for stronger and/or lighter bond connections. The IR absorbance trend in bonds, according to Exercise 4.8, can be rationalized by this concept, with single bonds absorbing at lower frequencies compared to double and triple bonds.