Pneumocystis carinii is an endemic protozoan that does not usually cause any illness in humans. P. carinii can cause a serious lung infection in patients:a. with a history of asthmab. with chronic obstructive pulmonary disease (COPD)c. with suppressed immune systemsd. traveling outside their normal environmentI want to say that it could be "c" combined with either "a" or "b"...I'm not sure what the best answer is. Does anybody have some input?