“Happy as a child”做主语“I”的补足语,还可以把它放在后面：I got on the bicycle and headed out onto the streets,as happy as a child.=I was as happy as a child when I got on the bicycle and headed out...但是语法规则说不通啊，怎能又形容词+介词短语这种结构的？呵呵。。。