《For and Against》第16课有句话: They adopted a policy of neutrality, and while the rest of the world seethed in turmoil.问题:请问两个连词可以并用吗?and 和 while是否只用其中一个比如while 就可以了?
The city at one time must have been prosperous, for it enjoyed a high level of civilization.想问下这句话中at one time 都可以放在句子的什么位置,可以放在been之后吗?还有must have been 是推测的用法吗,可以详细解释一下吗,谢谢~