简单英语翻译。。。就3个

我们尽力使那位紧张的老相信乘飞机是安全的。
We tried our best to assure the nervous old man that it is safe on the plane.

tried our best ----> 尽我们最大的努力。 还有就是safety是名词，安全的意思，要说安全的的话就要用safe。 （其实这个造句用reassure更好一点，有安慰，使某人相信的意思）

很多母亲试图在她们的女儿身上实现她们的梦想。
Most mothers try to achieve their dreams through their daughters.

恶劣的天气使人们不能去参加游行.
The bad weather discouraged people from participating in the parade.

attending虽然有参加的意思，但是一般都是指会议或是仪式，而游行之类的还是用participate比较好。

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希望对你有帮助~

第一句were 改成was;
第二句去掉to;
第三句没问题。

1.We try to assure the nervous old man of flying is safe. 2.Many mothers are trying to realize their dreams by their daughters. 3.The bad weather caused people can't join in the parade.

第一个把were safty改成was safe就可以了，flying是可以有来表明“乘飞机”的，在“百万宝贝”里就有这样的台词：we fly there,drive back,在这里用fly的动词形式，用名词表明状态。
第二句：Most mothers try to achieve their dreams by their daughters.
第三句：the bad weather discouraged people from parade。discourage...from doing sth,from 后一定接名词，意思是阻止， 阻拦某人做某事，在此处，parade可用做名词。