______on ten years of observation and study, Professor Wang announces that everyone dreams every night, whether they realize it or not.
After you have used the dictionary, please just put it back ____it belongs.
It is usually not quite cold in this area in March, but sometimes temperature be very low.
--__________ was it_________ they discovered the entrance to the underground place? --Totally by chance.
The amount of money _____for the seriously sick child was soon collected.
Their tent,__________ light as a feather, remained firm in the storm last night.