Điền quan hệ từ thích hợp

___she saw the handwriting on the anonymous letter, she knew who had sent it to her
2. though cholera is spead____directly or through flies and waste, water is the chief medium for spread of this disease
3. you should tell him about the difficulties you are having,___, he will assume that you are doing well with the project
4. you should encourage your child to eat all foods___he will get a well-balanced meal
5. the price of oil and oil products began dropping drastically at the beginning of 1998___famous, large oil companies were cutting back drastically