Definition: Given a scientific passage and an answer, generate a question for the given answer.
Input: Passage: Plants alternate between diploid-cell plants and haploid-cell plants. This is called alternation of generations , because the plant type alternates from generation to generation. In alternation of generations, the plant alternates between a sporophyte that has diploid cells and a gametophyte that has haploid cells. Answer: alternation of generation
Output:
When plant type alternates from generation to generation what is this called?