被英语里的and前面的逗号整糊涂了,请教英语达人.
第一句话：Being optimistic can enable people to behave wisely,kindly and confidently,and it is crucial for any individual's ,in terms of both character and competence.（,and有个逗号）
第二句话：The title of the movie is The Legend of 1900 and there are some reasons for my recommendation.（ and前没逗号）
第三句话：With optimism,the goal we set can be reached ,and the hard nut can be cracked.( ,and前有逗号)
这里的and前的逗号或不加逗号,难道仅仅就是为了看起来简短或整齐吗?有没有语法上的讲究呢?