Hawking became world-famous in _______.his thirties in the 1970’s the thirties in his 1970his 30s in 1970’sthe thirties during the 1970
On April 1, Jim tried to play a trick ______ his teacher but the teacher wasn’t taken _____.
Many children seldom communicate with adults, ________ it difficult for their parents to know what they are thinking about.
The headmaster demanded all the teachers ______ in the office.
—How was that? —I was chatting on line ______ the power went out.
In order not to be disturbed, I spent three hours _______ in my study.