Scientists think that the continents ________ always where they ________ today.
A.aren't; areB.aren't; wereC.weren't; areD.weren't; were在线课程C
由第二个空的时间状语today可知第二个空应使用现在时态，故淘汰B、D两项，又因为句子内容是在把不同时期的continents的位置进行对比，因此应选择C项。