They aren't serious enough.他们不够严肃。 enough 足够
①形容词+enough 如:{#blank#}1{#/blank#}足够漂亮
②enough+名词 如:{#blank#}2{#/blank#} 足够食物
I have {#blank#}3{#/blank#} go to Beijing. 我有足够的钱去北京。
③形容词+enough to do sth.足够……去做…… 如:
She is {#blank#}4{#/blank#}go to school.她到了上学的年龄。