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

Ex Input:
Passage: Plants in the haploid generation are called gametophytes . They form from haploid spores. They have male and/or female reproductive organs and reproduce sexually. They produce haploid gametes by mitosis. Fertilization of gametes produces diploid zygotes. Zygotes develop into the diploid generation. Answer: through mitosis

Ex Output:
How do gametophyte plants form haploid gametes?

Ex Input:
Passage: A variable is a factor that can change over the course of an experiment. Independent variables are factors whose values are controlled by the experimenter to determine its relationship to an observed phenomenon (the dependent variable). Dependent variables change in response to the independent variable. Answer: independent variables

Ex Output:
The values of which factors are controlled by the experimenter over the course of an experiment?

Ex Input:
Passage: Ebola is a rare and deadly disease caused by infection with a strain of Ebola virus. The 2014 Ebola epidemic is the largest in history, affecting multiple countries in West Africa, including Guinea, Sierra Leone and Liberia. Ebola is spread through direct contact with blood and body fluids of a person infected by and already showing symptoms of Ebola. Ebola is not spread through the air, water, food, or mosquitoes. See Ebola virus disease at http://www. who. int/mediacentre/factsheets/fs103/en/ for additional information. Answer: virus

Ex Output:
Ebola is an example of a disease spread by what kind of infectious agent?