Sam _____ some knowledge of the computer just by watching others working on it.
British adventurer and swimmer Lewis Gordon Pugh became the first person to swim in the icy waters of North Pole,to raise awareness of how global warming ______ the polar ice cap.
Considering the coming of the entrance exam,some schools have abandoned the ______of doing morning exercises.
The teacher told the monitor to ______ all the students' names who were absent from class.
John may phone tonight,I don't want to go out ______ he phones.
He is always helping people without expecting anything ______.