1. Tony learned a lot since he started this English course.->has learned form : S + present perfect simple (HTHH),... since S + past simple (QKĐ),....
2.They can play badminton. I can play badminton, either.- > too
1. Tony learned a lot since he started this English course.
learned -> has learned
2. They can play badminton. I can play badminton, either.
either -> too