Theconceptofmaglevtransportationwas

問題詳情：

 The concept of maglev transportation was ______first presented in the mid-20th century and the first commercial maglev train line was put into ______ operation at Birmingham Airport in Britain in ㊣1984

A. the; the        B. the; /                 C. /; the          D. /; /                 

【回答】

D

知識點：冠詞

題型：選擇題