Final answer:
The percentage of their offspring expected to be black is 0%.
Step-by-step explanation:
The answer to the question is b) 25%. When a calico cat mates with an orange cat, their offspring can have a variety of coat colors. However, black coat color is not expected to appear in this cross, as it requires a specific combination of genes that are not present in either parent. Therefore, the percentage of offspring expected to be black is 0%, not 25%.