__when we passed by its nest.
Evidence has been piled up ________ drinking water after getting up in the morning contributes to one's health.
It is usually thought ________ a little child says is truth.
The warning we were given as children ________ eating fast will make you fat, may in fact, have a scientific explanation.
Although Anne is happy with her success, she wonders ________ will happen to her private life.
________ there are living creatures in the outer space as those on Earth hasn't been proved until now.