Analyze the effects of infrared radiation on molecular bonds and identify the type of transition it causes.

• A. Infrared radiation causes electronic excitations, affecting valence electrons.
• B. Infrared radiation causes nuclear spin transitions, affecting atomic nuclei.
• C. Infrared radiation causes molecular rotations, affecting rotational energy levels.
• D. Infrared radiation causes molecular vibrations, affecting bond lengths and angles.

Answer: (D)