根据汉语意思完成句子。

1)She failed in the exam. That was _____she didn't study  hard.她考试不及格，那是因为她学习不努力。

2)She didn't study hard. That was _____she failed in the  exam．她学习不努力，所以考试不及格。3)The reason why she hasn't come is _____she has to take  care of her sick mother.她没来的原因是她必须照顾她生病  的妈妈。