It is ___ to observe traffic rules.
The city ______ by an army of 600 men was difficult to take.
At the meeting they discussed three different ______ to the study of mathematics.
He sat back on the chair, listening to the MP4 and ______.
Living in the dormitory means ______ to take care of yourself, understand each other’s differences and share ______ interests.
People have always ______ about exactly how life on earth began.