As is known to us, theory is based on practice and _____ servers practice. A. by chance B. in turn C. in return C. by turn
You should ___ the lights if there is no one in the room.
Save water as ___ as we can.
--What’s the time ___ your watch?---On, my watch ___ “A quarter to five”
--____ did he send this letter to you? ---By mail
--Let’s go to see our teacher. ---_____.