1.while my former teacher had been patient with all the students,my new teacher quickly punished those who gave a incorrect answers.
这个句子里的had been 怎么讲?如果是过去完成时,后面怎么没动词?
2.I worked hard to meet the minimum standards set by the course and to complete assignments on time.
这里的set是什么意思
3.it is critical that students feel comfortable expressing themselves in writing.
expressing前面是不是省略了一个介词in