单项选择题
The police found that George had still another （）of income
A. origin B. source C. basis D. means
单项选择题 The doctor suggests that a person （） exercises every day if he wishes to be healthy.
单项选择题 It was from Stephen （） she first heard of the man referred to as a specialist
单项选择题 When I was a child I used （） swimming in the lake.
