As is known to all language learners, newly learnt words will soon be forgotten unless ______ used in everyday communication.
The fresh air _____ our health and we _____ it.
______ as an Olympic event, a sport must be played in at least 75 countries in at least 4 continents.
At the meeting they discussed different ______ to the study of mathematics.
The children were warned of not being too _______ about things you are not supposed to know.
I keep in touch with the friend ______ who stands ______ to me.