对于直列4缸发动机而言，点发火次序一般有（）。
A.1-2-3-4
B.1-3-4-2
C.1-2-4-3
D.4-2-3-1
参考答案：B, C
The students the Art Festival when I passed by their school.
A．celebrate
B．were celebrating
C．will celebrate
D．have celebrated
选择填空。
______ often helps ______ with ______ English. [ ]
A. His; her; hers
B. She; him; his
C. She; him; her
