What is a first broad layer of watercolour commonly called?

Correct answer: Wash

The governing concept is a broad, diluted and transparent application of watercolour. A first overall layer spread across a large area is commonly called a wash, so option A is correct. It establishes a light base before later details are added. A glaze is a transparent layer usually placed over a dry layer to modify colour, dry brush uses little water for texture, and impasto is thick raised paint, not typical watercolour practice.