These stamps are very （valuable,珍贵的）.You must keep them well.
We must (pull down,推到) the old house.
Germs can (enter,进入) the human body through the mouth.
Since then,people (regard,视为) the Great Wall as a symbol of the Chinese nation.
A (quarter,四分之一) is another way of saying 15 minutes.
The Great Pyramid is one of the seven (wonders,奇观) of the ancient world.
My bike is broken.Can you (mend,修理) it?
This club is for (youths,青少年).
Could you buy some (snacks,小吃）?
We must keep (ecological balance,生态平衡）.
I think (eating habits,饮食习惯） are important for our health.
I learned a lot of (knowledge,知识) about English.
I often go swimming during the summer (vacation,假期).
We have a (friendship,友谊) of 20 years.
They wanted to (share,分享) each other.