作业帮had been puzzled over the problem for over an hour without any resultI had been puzzled over the problem for over an hour without any result,________ all at once the solution flashed across my mind.A whileB whenC then D as 应该选B.为什么?各个
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had been puzzled over the problem for over an hour without any resultI had been puzzled over the problem for over an hour without any result,________ all at once the solution flashed across my mind.A whileB whenC then D as 应该选B.为什么?各个
had been puzzled over the problem for over an hour without any result
I had been puzzled over the problem for over an hour without any result,________ all at once the solution flashed across my mind.
A while
B when
C then
D as
应该选B.为什么?各个选项都讲一遍为什么不对.
had been puzzled over the problem for over an hour without any resultI had been puzzled over the problem for over an hour without any result,________ all at once the solution flashed across my mind.A whileB whenC then D as 应该选B.为什么?各个
我已经对这个难题思考了一个小时还是没有结果,正在这时答案有我的头脑中显现!
when翻译为正在这时（有突然发生的意思）,这是它的特殊用法!
while ,as充当时间状语时只能表示一边一边故代入句子明显不和理!
then那时代入句子,得到翻译结果：
我已经对这个难题思考了一个小时还是没有结果,那时答案有我的头脑中显现!（那时答案已经有了,还用思考一个小时吗!）
有这里when的用法如下：
表示前面的叙述所没有提到过的信息.它总是对所描述的事件予以引人注目的强调,意为“这时；突然”；当位于句末的分句具有引种用法时,大致有以下三种情况：
A.when 分句前面的分句使用过去进行时.
如：（ 1 ） He was still smiling when the door opened and his wife came in.他正笑着的时候,门突然开了,他妻子走了进来.
（ 2 ） I was thinking of this when I heard my name called.我正想着这件事时,突然听到有人叫我的名字.
B.when 分句前面的分句使用 was （were） about to,was （were） on the point 等.
如：（ 1 ） We were about to start when it began to rain.我们刚要出发就开始下雨了.
（ 2 ） He was on the point of leaving when someone knocked at the door.他刚要走就有人敲门.
C.when 分句之前的分句用过去完成时,其中 sb had hardly / scarcely /barely … when 已成为固定词组.如：
（ 1 ） We had hardly fallen asleep when the bell rang.我们刚刚入睡,铃声就响了起来.
（ 2 ） He had scarcely arrived when he had to leave again.他刚刚到达就又要离开了.