(Plz help) Name the element of art that was a chief measure of excellence in Chinese painting and how it
was successfully used

I think this is the answer you are looking for:

The element of art that was a chief measure of excellence in Chinese painting was the quality of the bush line. It was successfully used by Han Gah when a delicate use of line was combined with subtle value gradation to give the animal a realistic appearance.

Subo tite muna

Explanation:

they are often in theme and variations

hi     (had to add 20 words)