Question

mechanical ventilation is necessary to: help prevent grease build - up on walls reduce odours which could attract pests remove heat, steam, and fumes from the kitchen all of the above

Explanation:

Mechanical ventilation helps in preventing grease build - up (by removing vapors that carry grease), reducing odors (as it expels odor - containing air) and removing heat, steam and fumes (as it replaces the air in the kitchen with fresh air). So all the given functions are valid for mechanical ventilation.

Answer:

D. all of the above