单项选择题
He was（）the preparation of an international conference when I arrived in Beijing.
A.engaged to B.engaged for C.engaged on D.engaged in
单项选择题 The population of the earth（）increasing fast. One third of the population here（）workers.
单项选择题 He, as well as I,（）a student.
单项选择题 She comes from（）people's Republic of China.
