Final answer:
The probability of the offspring being light yellow (WY) when two light yellow flowers (WY) are crossed is 50%, since each parent can contribute either allele with equal probability.
Step-by-step explanation:
When two light yellow flowers are crossed, the probability of the offspring being light yellow can be determined using Mendelian genetics principles. Assuming that light yellow (WY) is a result of incomplete dominance, where W is the allele for light yellow and Y is recessive, we can expect the following. If each parent is WY, the possible genotypes for the offspring would be WW, WY, WY, and YY. Using a Punnett square, we find that there is a 50% chance (WY from one W parent and Y from the other, and vice versa) the offspring will inherit the WY genotype, and therefore be light yellow. Thus, the correct answer is b) 50%.