原式=(-60)×34+(-60)×56-(-60)×1115-(-60)×712
=-45-50+44+35
=-16.
The flu is believed _______ by viruses that like to reproduce in the cells inside the human nose and throat.
A.causing
B.being caused
C.to be caused
D.be have caused
公债的特征不包括()。
A.有偿性
B.自愿性
C.灵活性
D.多样性