Ask your classmate if the he/she was in Great Britain , at the Zoo, in the Shop last summer (week,month),2 days ago.
Example:Were you in Great Britain last year? -Yes , a was.
When were you there ?-Last spring.

-Were you in the zoo last week?-Yes, I were. -Were you in the shop yesterday?-No, I weren't-When were you there?-last week