serious的比较级和最高级分别为more serious和the most serious。serious作为形容词，意为不好的、严重的、有危险的、严肃的、重要的；more serious作为比较级，意为更严重的；the most serious作为最高级，意为最严重的。
serious为形容词，意思有不好的;严重的;有危险的;需认真思考的;严肃的;重要的;须重视的。它的比较级为more serious，最高级为the most serious。例句：
1、They pose a serious threat to security.
他们对安全构成严重威胁。
2、It's time to give serious consideration to this matter.
到了认真考虑这一问题的时候了。
3、The team is a serious contender for the title this year.
该队是今年不可轻视的夺标竞争者。
4、I'm afraid I'm not a very serious person.
恐怕我不是一个非常严肃的人。
5、Is she serious about wanting to sell the house?
她真想把房子卖掉吗？
more serious作为serious的比较级，意思有更严重的、更严肃的、更郑重的。例句：
1、Loss of health is more serious than loss of wealth.
健康的丧失比财富的损失更为重要。
2、It wouldn't hurt you to be a bit more serious.
认真一点对你没有坏处。
3、The weight loss began to look more serious
体重下降眼看开始变得愈发厉害了。
4、The more serious flashpoints are outside the capital.
更加危险的动乱区在首都之外。
the most serious作为serious的最高级，意思为最严重的。例句：
1、Nutrient problem is one of the most serious problems.
营养问题是最严重的问题之一。
2、This is the most serious issue.
这才是最紧要的问题。
3、This is the most serious problem ( that) we have ever met.
这是我们遇到过的最严重的问题。
4、The most serious effects are on the lungs, which is usually the cause of death.
最严重的影响是对肺部，这是通常的死亡原因。
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