_______ basic first-aid techniques will help you respond quickly to emergencies.

nobody gave him any help, he ________ have done the research on his own.

填入下面一段文字横线处的语句，最恰当的一句是（ ）我们都会衰老。我镇定的注视着我的年纪，犹如眺望远方一副渐渐逼近的白帆，为什么要掩饰这个现实呢 。勇气不是储存在脸庞里，而是掌握在自己手中。

It is usually warm in my hometown in March, but it _____ be rather cold sometimes.

We work together to achieve our common purpose: __________ world that is safer, cleaner and healthier than __________ one we are living in.