Write the correct present perfect verb form in the following sentences:
1. We?______
(study) for the exam for a week.
2. Since last week, he _____
(write) five pages of his novel.
3. She____
_(fall) many times since she started Rollerblading.
4. For many weeks, the jury_____
(hear) testimony.
5. Since last year, Carl______
. (feel) happy at work.
6. Michelle______
- (sleep) late since she was a teenager.