Could we see everything? (-ve)
No, we couldn't.
Could they play the instruments well? (-ve)
No, they couldn't.
Could he dance well? (+ve)
Yes, he could.
Could he play the guitar? (-ve)
No, he couldn't.
Could he mix and scratch the records well? (+ve)
Yes, he could.
Could they take photos at the concert? (-ve)
No, they couldn't.
Could he play the guitar?
No, he could play the drums!
Could she play the violin?
No, she could play the saxophone!
