1、My suggestion is more attention should be attached to the issue of youth drug abuse.
*is是系动词,后跟表语从句,that引导表语从句时不能省略,这里少了that.
*主语是suggestion,advice等表示建议,命令的词从句应当用虚拟语气,并且should要省略.
2、People think developing space research well spend a huge number of money.
*spend表示花费时间或金钱时主语应当是支付者,是人,cost的主语才是物,这里是说发展太空研究会花费大量金钱.主语是物,应该改成cost.（will打错咯!）
*a large/huge/great number of只能修饰可数名词,money不可数,所以错了.改成huge amounts of吧.
3、Now people go abroad becomes very easy.
*这句句子有两个动词,肯定不对,become是真正的动词,句子意思是现在人们出国变的很容易.要不然就把become前面的部分变成主语从句,用that引导,That people go abroad now becomes very easy.要不然就把它变成动名词短语,就可以做主语了.Now people's going abroad becomes very easy.
4、When one is over 70 years old,he is very dangerous if left alone at home.
*当人超过70岁的时候,一个人独自在家是很危险的.错在he is very dangerous,他不是怪兽啊,怎么能说他很危险呢?所以应该改成it is very dangerous if he is left alone at home.it是形式主语,真正的主语是if he ...并且这里if从句当中的he不要省略,否则从句的主语都不知道到哪里去找拉~.
回答完毕,不懂再问^^