I rang the doorbell several times but I couldn’t make anyone .

The specialist, ______ some of his assistants, ____ to attend our discussion.

Are you free after school? —Sorry, I’ve planned to treat a friend of mine to dinner___for his help

ee, I’m poor in physics and you arenot good at chemistry, and……— That’s _______ we should help each other

The father as well as his three children ___skating on the frozen river every Sunday afternoon in winter.