Given a scientific passage and an answer, generate a question for the given answer.

Example Input: Passage: The mass number is the number of protons plus the number of neutrons in an atom. For example, most atoms of helium have 2 neutrons, so their mass number is 2 + 2 = 4. This mass number means that an atom of helium has a mass of about 4 amu. Answer: protons and neutrons
Example Output: What makes up the mass number of an atom?

Example Input: Passage: Structure of the trp operon. The trp operon is composed of 5 structural genes, 1 regulatory gene and other regulatory sequences, including the promoter, operator and leader sequence. Within the leader sequence is the attenuator region. In the presence of tryptophan, the structural genes are not transcribed. Answer: they are not transcribed
Example Output: What happens to structural genes in the presence of tryptophan?

Example Input: Passage: Plants are multicellular eukaryotes with cell walls made of cellulose. Plant cells also have chloroplasts. In addition, plants have specialized reproductive organs. These are structures that produce reproductive cells. Male reproductive organs produce sperm, and female reproductive organs produce eggs. Male and female reproductive organs may be on the same or different plants. Answer: plant cells
Example Output:
What type of cells have chloroplasts?