...Not until the 1980's did some concerned citizens in Beijing started to find ways to preserve historical buildings from destruction.
as far as one is concerned
这三个里面的concerned都是什么意思，怎么区分？concerned与concerning的区别？
He would have finished his college education, but he (C) to quit and
find a job to support his family.A had hadB hasC hadD would havewould have finished 是过去将来完成时吗，还是虚拟语气，表示与现在事实相反but后面那一句是真实的句子.
Where is Paul’s family going over the holiday?这是2019版人教版高中英语新教材必修一的 Unit 2（p24）的句子。请问为什么用介词over，可以改用in, on 吗？over the holiday, on the holiday, in the holiday有什么区别？
Fossil charcoals tell us that wildfires have been part of life on Earth for as long as there have been plants on land. That's m ore than 400 million years of fire.
She wants to know whether the measures have been agreed ( ).A. toB. withC. aboutD. uponE. over答案是D.upon (=on). 但是我很奇怪和不解：A. to, B. with, C. about - 这3个选择不也可以吗？
...ll the fresh sweet milk in the pail that she had learned to carry balanced on her head.As she went along, she began thinking about what she would do with the money she would get by selling the milk.这段话里的 learned to carry balanced on her head. 是什么意思?
Vietnam said 8 of its ships had been rammed and fired on by water cannon as they approachd a Chinese oil drilling ship off the disputed Paracel islands.其中 a Chinese oil drilling ship off the disputed Paracel islands.中的 off 是什么意思？是远离的意思吗？
...erica's steel mills in 1952 rather than allow a strike to imperil the conduct of the korean war has washington toyed with nationalization,or its functional equivalent,on this kind of scale.