.I used to ______ a lot of time __________ games with my friends.
We must do everything we can _____ our earth cleaner and safer.
----- I’m going to visit my aunt this weekend. She was very kind to us when we were at her home last time, remember? -----Of course I do. _______.
----- I forgot my mother’s birthday! -----_______ You’d better keep it in mind next year.
----- How soon will you start your journey? -----I’m not sure. I haven’t decided ________.
I never doubt ______ the science museums are worth_______.