1. The problem statement, all variables and given/known data In order to produce a sustained interference pattern by light waves from multiple sources, which of the following conditions is sufficient? a. the sources are coherent b. the sources are monochromatic c. no more than two sources are allowed d. three or more sources are required e. none of the choices above are valid 3. The attempt at a solution This question seems messed up to me. From what I understand, both A and B can be correct. I am totally confused. please help if you can, thanks.