一道关于英语强调句的题目It was not until world war II broke out ___ the

其实强调句与状语从句很容易区分
你把“it is ”和“that”都去掉,再看看剩下的句子是否完整就可.
就上面两个题来说
1.the young man didn't leave his home town to fight against the enemies until world war II broke out .
去掉“it is ”和“that”,句子仍是完整的.这就说明是强调句,强调句只是起一个强调作用,不改变句子本身的成分.
2.可先将疑问句还原
it was 5o'clock ___ he arrived.
如果选“that”,看做强调句.那去掉“it was ”和“that”
he arrived 5o'clock 不是完整句子 应为 he arrived at 5o'clock
所以是when引导的状语从句

强调句的确不能用when 只能用who/ that
Was it 5 o'clock when he arrived?是时间状语从句

对not…until句式的强调有固定的句型，即It is / was not until…that,所以不选when.
你说的Was it 5 o'clock when he arrived?是一个定语从句.
我们说的强调句通常有下面几种类型:
1．用助动词“do（does／did）＋动词原形”来表示强调
2．用形容词 very，only，single，such...

所谓强调句就是强调时间，地点，原因，人物等，句型就是it was…that…判断出是强调句后就可以做了。下一题如果是强调句应该要加上at才对 at 5 o'clock 。因为强调的是时间所以强调部分的句子介词at不可少，所以此句不是强调句，理解了不