What should be done for the next glaze if a dried layer appears darker than expected?

Correct answer: Make the next layer thinner or omit it

In watercolour, each transparent glaze adds pigment and can deepen the value after drying. If the existing layer is already too dark, the next glaze should be diluted with more water or omitted in that area. D is correct because it prevents further darkening. More concentrated paint and black would worsen the value, while opaque white would abandon the transparent-glazing method.