If light blue becomes too pale what should be done to make it bluer?

Correct answer: Increase the base blue slightly

The governing concept is correcting a weak tint by increasing its base hue. If light blue is too pale, adding a small amount of the original blue pigment strengthens the blue identity while preserving the same general hue. Thus, option C is correct. More white would make the mixture paler, yellow would shift it toward green, and much black would make it darker and duller rather than cleanly bluer. The base blue should be added in small increments, with mixing between additions, so the desired intensity is reached without overshooting.