下面式子中，不是方程的是[ ]
A.x =5
B.0.1x =5
C.5x =0.1
D.5x >1
答案：D
After ________ an international school bus exhibition in Beijing, Susan painted her dream school bus. [ ]
A. having been visited
B. to visit
C. visited
D. visiting
在三相四线制电路中，三个线电流之和等于零。 （）
