When travelling in buses or trains, we are likely to have conversations _____ we give information or opinions about different things.
The two balls fell ________the same speed and landed ________the ground at the same time.
After many years of hard work,Mary and her husband had at last paid ________all the money they had borrowed.
They thought the meeting was ________great importance.
________the birthrate down by 10%,the number of the population has decreased.
The army went ________the thick forest and at last came to a little river.