Which of the following would be an environmental factor that could affect gene expression? (1 point)

The environmental factor that could affect gene expression from the options provided is temperature of the water. Temperature can influence metabolic processes and the expression of certain genes in organisms, particularly in ectothermic animals. The other options listed (sex of the organism, organ of the organism, and number of organisms in the group) are more related to genetic and biological factors rather than environmental ones.