good
［误］ I've been waiting for good twenty minutes.
［正］ I've been waiting for a good twenty minutes.
［析］ a good之意为"足足"、"整整"之意。
good well
He is good. 应译为"他是个好人。"而He is well. 应译为"他身体不错。"I feel good. 即精神状态良好，而I feel well.即身体状况不错。
［误］ This food is very good to you.
［正］ This food is very good for you.
［析］ be good for是"对……有利、有好处"，而be good to是指"对待某人不错"，如：Your friend is very good to me.
grade
［误］ -What grade are you in? -I'm in grade 1.
［正］ -What grade are you in? -I'm in Gread 1.
［析］ 当泛指那一年级时grade的头一个字母小写，当有具体数字时则要大写。