He bought a house for his children ________
B
本题属于动词不定式复合结构做后置定语。in不可省略。句意:他买了一套房子给孩子们住。
So far scientists have only acquired ________ understanding of the physical processes that cause earthquakes.
_______ at all is worth doing well.
The traffic was held up for more than thirty minutes, ________ caused me to arrive late.