The central tenet of gestalt psychology is that the whole is different from the sum of its parts. what does this mean in the context of perception?

perception is an hollistic process, it is more than the mere sum of its parts

Explanation:

The interconnected parts organize themselves and our brain then reinterprets them in a new way focusing in the whole according to these principles.

Some deliberately use them, as many visual artists, for example take advantage of the perceptual phenomena (continuity, closure,etc) in order to portray a complex representation.

Notice how some small details are integrated as a whole,

The image below is an example by Salvador Dali  1941:

answer; /// the correct answer is (a) burned the city;

taking a bath requires the most water out of the given options because it takes a significant amount of water in order to fill a bathtub.