英语写信格式时的称呼,是首字母大写还是全部首字母大写呢?

1。"Dear students; Dear teachers; Dear parents。。。" 仅第一个字母大写。2。我的家人有我的父母们和我的妹妹和弟弟:(a) My family members are my parents,a sister and a brother。(b) There are five members in my family:Myself,my parents,a (younger) sister and a (younger) brother。