完成句子：根据所给汉语意思，用单词或短语完成下列英文句子。（共5小题，计10分）我爷爷七十岁了，但看起来依然帅气。
My grandfather is 70, but he still .我们每年三月植树。
We plant trees every year. 如果你不知道事实，请保持沉默。
If you don’t know the truth, please keep . 请访问我们的网站，来购买特别的礼物。
Please visit our website to .多么有用的词典啊！
What they are!
________（thousand）of students rushed out to celebrate their victory（胜利）．
They expected that they could solve the problem by________（they）．
________（polite），he drove the old man out of the room and shouted at him angrily．
Be careful to cross the street when we meet heavy________（traffic）．