What can be done next time if watercolour dries lighter than expected?

Correct answer: Prepare a slightly darker mixture while wet

The governing concept is value adjustment for the normal lightening that can occur when watercolour dries. If a trial patch becomes too pale, prepare the next wet mixture with slightly more pigment or a little less water, then test it again before covering the main area. Option A is correct because it anticipates the drying shift. Adding more water would usually make the wash lighter, and changing paper or adding only white is not the necessary solution.