自2010年至今的四级考试中， 共出现过 次
自2010年至今的六级考试中， 共出现过 次
N-COUNT 信;信函 If you write a letter to someone, you write a message on paper and send it to them, usually by post.
I had received a letter from a very close friend.
...a letter of resignation...
N-COUNT 字母 Letters are written symbols which represent one of the sounds in a language.
...the letters of the alphabet.
...the letter E.
N-COUNT （校队队衣的）校名首字母标志（以嘉许优秀运动员） If a student earns a letter in sports or athletics by being part of the university or college team, they are entitled to wear on their jacket the initial letter of the name of their university or college.
Valerie earned letters in three sports: volleyball, basketball, and field hockey.
VERB 赢得佩戴校名首字母标志的荣誉 If a student letters in sports or athletics by being part of the university or college team, they are entitled to wear on their jacket the initial letter of the name of their university or college.
Burkoth lettered in soccer.
PHRASE （钻）法律字眼 If you say that someone keeps to the letter of the law, you mean that they act according to what is actually written in the law, rather than according to the general principles of it, especially when you disapprove of this.
They had stuck to the letter of the law and in my view they should be ashamed.
PHRASE （执行指示）毫厘不爽地，不折不扣地 If you say that someone carries out instructions to the letter, you mean that they do exactly what they are told to do, paying great attention to every detail.
She obeyed his instructions to the letter.