Answer:
Compound A: Benzoyl chloride
Compound B: Benzaldehyde - (tBuO)₃Al complex
Compound C: Benzaldehyde
Compound D: Benzyl alcohol
Explanation:
The lithium tri-tert-butoxyaluminum hydride that the first student used is a milder reagent than LAH and will stop reacting at the aldehyde.
The LAH that the second student used is much more reactive and will continue to reduce the benzoic acid as far as possible, going all the way to the alcohol.
See the attachment for the reaction steps.