唯物辩证法是一个完整的科学体系，作为一个理论体系，其核心是（）。
A.联系的观点
B.发展的观点
C.对立统一规律
D.质量互变规律
参考答案：C
Beethoven was walking in the street _______ he heard someone ________ his music. [ ]
A. before, play
B. after, playing
C. when, playing
D. while, to play
慓疾滑利之气是指
A．元气
B．宗气
C．卫气
D．营气
E．中气
