Use the Simple Past or the Present Perfect. 1. Since classes

Use the Simple Past or the Present Perfect. 1. Since classes began, I (have, not) much free time. I (have) several big tests to study for. 2. Last night my roommate and I (have) some free time, so we (go) to a show. 3. I admit that I (get) older since I last (see) you, but with any luck at all, I (get, also) wiser. 4. The science of medicine (advance) a great deal in the nineteenth century. 5. Since the beginning of the twentieth century, medical scientists (make) many important discoveries.