23.The modern technology to shrink(缩短) the distances of runways which large and fast aircraft use.a.has begun b.have begunc.began d.had begun12.Once you the brand of whisky,you will never want to drink any other.a.drunk b.have drunk c.will drink d.drank17.He was disappointed that all of the guests when he at the party.a.left,had arrived b.left,arrivedc.had left,had arrived d.had left,arrived18.How long you the army till now?a.did,join b.have,joined c.
23.The modern technology to shrink(缩短) the distances of runways which large and fast aircraft use.
a.has begun b.have begun
c.began d.had begun
12.Once you the brand of whisky,you will never want to drink any other.
a.drunk b.have drunk c.will drink d.drank
17.He was disappointed that all of the guests when he at the party.
a.left,had arrived b.left,arrived
c.had left,had arrived d.had left,arrived
18.How long you the army till now?
a.did,join b.have,joined
c.have,been d.have,served in
–Nancy is not coming tonight.
A.promises B.promised
C.will promise D.had promised
..为什么啊- -..
23、定语从句前后时态应该一致，根据前文主语，应选择第三人称单数形势的谓语。
12、once引导的从句，主句是将来时，从句用现在是，包括一般现在时、现在完成时等。
17、“他到时客人们都走了”，客人走在前，他到在后。整个句子都是过去时态，所以前面过去完成，后面一般过去。
18、till now提问一个时间段，所以问句应是时间段。join是点动词，been+in才对。
最后一题：Nancy没来，但是她答应了（要来）。已经答应了，所以应该过去时或者完成时。
1."which large and fast aircraft use"表示现在时态,原句意思表示已经开始了,所以是现在完成时2.个人认为应该是一般时,“主将重现”语法.但是没有一般时.只能是完成时,意思是“一旦你尝过威士忌,你将不想要其他的了...