学习笔记：
★father：爸爸
例句：His father was a professor of medieval studies. 他的父亲是研究中世纪历史的教授。
★mother：妈妈
例句：He recognized his mother's handwriting on the envelope. 他认出信封上他母亲的手记。
★brother：哥哥
例句：Must your brother tag along with us everywhere we go? 你兄弟干吗总紧跟着我们？
★sister：姐姐
例句：She was intriguing with her sister against her mother. 她和妹妹串通捣鬼和母亲作对。
★baby：婴儿
例句：I must mind the baby while Mum goes to the shops. 妈妈去买东西时我必须照看这婴儿。
