... Unit 9 -10 English 128. You ___ ring the bell; I have a key.A. mustn’t B. needn’t C. couldn’t D. shouldn’t9. It must ___ without delay.A. be done B. have been done C. do D. be doing 10. By ... therefore2. I am going shopping for food this evening, ________ I do not have to go at the weekend.a. so b. but c. however d. moreover Exercises Unit 9 -10 English 123. We live in the same building, ... Indian music and jazz. It ___ tell the difference between Indian music and jazz. Exercises Unit 9 -10 English 12BUT, SO, HOWEVER and THEREFORE Exercise 1: Add so, but, therefore, however where appropriate....