Flu is a very ______ infectious disease. Fever, headaches, coughing and fatigue are some of its ______ symptoms.

A．normal; common

B．usual; ordinary

C．common; usual

D．ordinary; normal

中医学关于“证候”的概念是

A．对疾病症状的认识
B．阴阳失调的外在表现
C．对疾病体征的辨证认识
D．对疾病某一阶段的病理概括
E．体征与症状的综合表现