1.His parents have great ______{influence} over him.根据括号里的单词

1.His parents have great ______{influence} over him.根据括号里的单词在横线上写出正确形式.
2.It takes hard work _____{实现}success.
3.You don't seem to have any _____ {原则}.
4.I have known David for more than 20years.{改为同义句.}
I have known David for _____ 20years.{横线上只填一个单词}.