由地球自转运动产生的地理现象是（ ）
A．昼夜更替
B．极昼现象
C．四季变化
D．昼夜长短变化
地球自转产生的现象是昼夜交替和时间差异．
故选：A．
________ the moment they heard the starting signal given by the teacher. [ ]
A. Ran the children down the hill
B. Down the hill did the children run
C. Down the hill ran the children
D. Down the hill the children ran
下列图标表示（）电压等级。
A.10kV
B.110kV
C.1000kV
