What percentage of the offspring will have the dominant phenotype when two heterozygous individuals mate?

This type of cross is used vary often in tests and examples.The crossing of two heterozygous individuals always results in what is called a 1:2:1 ratio. This means that 1 of every four offspring (25%) will be zygous dominant, 2 out of every four offspring (50%) will be heterozygous, and 1 out of every four offspring (25%) will be zygous recessive. From this you can see that only 25% of the offspring will be zygous recessive. The other 75% are either heterozygous or zygous dominant, which both result in a dominant phenotype, so the answer to your question would be d.