Mary is rich, _____ I am poor. * a. if b. while c. when   This is a required question 12. We waited _____ he finished his homework. * a. although b. before c. until 13. They received a high mark on their exam _____ they had studied hard. * a. because b. as soon as c. whereas   This is a required question 14. I have played tennis ______ I was a young boy. * a. as long as b. since c. because 15. I saw Jack ______ I went to San Francisco. * a. even though b. the last time c. as long as ​