问题 big or small 用法疑问

There are many balls, big or small.这是什么用法？

问题 in being useful 怎么分析

... parted at night, she would have felt almost sure of success if he had not been to leave Hertfordshire so very soon. 请教老师：1）repaid her for the little sacrifice of her time. 这里的for怎么理解？2）in being useful 怎么分析，其中being如何理解？可以说成in her being us...

话题 Having been doing

话题 to have been

话题 Having been done

话题 have been doing

话题 must have been

话题 hadn’t been

话题 had been to

话题 Having been written

话题 might have been

话题 have been to

话题 had been carrying

话题 had been wrong

话题 would have been