... Exercises Unit 9-1 0 English 12 8. You ___ ring the bell; I have a key.A. mustn’t B. needn’t C. couldn’t D. shouldn’t9. ... music and jazz. It ___ tell the difference between Indian music and jazz. Exercises Unit 9-1 0 English 12 BUT, SO, HOWEVER and THEREFORE Exercise 1: Add so, but, therefore, however where appropriate. ... ________ I do not have to go at the weekend.a. so b. but c. however d. moreover Exercises Unit 9-1 0 English 12 3. We live in the same building, ________ we have hardly seen each othera. and b. therefore...