Final answer:
The question about the number of steps Cathy's dad built is incomplete and lacks context, making it impossible to determine the correct answer without additional information.
Step-by-step explanation:
The student's question about the number of steps Cathy's dad built does not provide enough information or context to determine the correct answer. When providing assistance, it is crucial to have the complete problem including any given data or conditions that may lead to a specific answer.
Without such information, any of the provided answers (a) 15, (b) 12, (c) 21, or (d) 25 could be valid depending on the unknown details of the scenario. Therefore, it is recommended that the student provides additional details or reviews the original question to ensure an accurate and helpful response.