Only when the customs barriers __________ can we enjoy free trade_英语解答

Only when the customs barriers __________ can we enjoy free trade and stage an economic take-off.
are abolished
have abolished
will be abolished
will abolish

人气：384 ℃　时间：2020-03-27 12:06:23

解答

are abolished
首先是要用被动语态,其次注意用一般现在时态来表示一般将来时态