Choose the sentence in each pair that is written correctly.
Example: a. I never been a good student.
✓ b. I have never been a good student.
24. a. Bob climbed a mountain when he was only 13.
b. Bob has climbed a mountain when he was only 13.
25. a. We taken the neighbor’s dog for a walk before.
b. We have taken the neighbor’s dog for a walk before.
26. a. Matt has gone to another country.
b. Matt has gone to another country last summer.