It generally complained of flu-like symptoms (headache, fever, muscle pain, sore throat) followed closely by stomach pain, vomiting, and diarrhea, which sometimes progressed to the bruising and hemorrhaging that he was seeing in his current patient.
Assume as what happens in a pot of water as it get heats.. hot becomes less dense, rises and cools, becoming more dense then sinks- that's called CONVECTION So D- is the right answer
