Kindly correct these sentences with explanation
1 Each furniture in this display is on sale for half price.
2 He is abusing the money of his father.
3 The duties of the secretary are to answer the telephone, to type letters and bookkeeping.
4 The models are not only less expensive but more efficient also.
5 He compiled with the requirement that all graduate students in education should write a thesis.
6 No sooner we left it began to rain
7 The population of Karachi is greater than any other city of Pakistan.