Адов,
Цитата:Well, I still have to make more mistakes like this before completely grasping the rule
I am afraid there is no actual rule here. Only some intuitive feeling which is extremely hard to put down in words.
It's more along the lines of "we would say it that way"/"we don't say it that way". We all three of us (I, Oleg2 and Ветер) are native speakers, we all would definetely use the imperfective, but it's rather hard to nail down the exact "why".
Цитата:I thought that the action is a specific one-time action, i.e. the cheating happened at the time of a certain exam, short and completed ... so used the perfective aspect.
As Oleg2 mentioned it, since someone is caught in the act of cheating, the act can not be completed. And if he is not caught, how anyone would know if it's taken place?
Вася списывал на экзамене, но его поймали. (He was trying to cheat, but was not successful in that. The act was not completed)
Вася попытался списать на экзамене, но его поймали/ Вася пытался списывать на экзамене, но его поймали (Here both aspects sound natural, though the action was not completed. Still I sense a subtle difference (maybe it's just me): the perfective has the sound of "He was trying to copy something from somewhere" (i.e. a narrower, more definite case), the imperfective simply describes his unlawful conduct "He was trying to cheat". Once again, I am not sure that it's not just me)
Вася списывал на экзамене, но преподаватель не заметил этого. (He was cheating at the exam, but the teacher hadn't caught him. We do not know how the cheating influenced his marks, whether it helped him or not.)
На экзамене Вася списал ответ из учебника. (He was successful in copying the answer from the book - a more definite case of cheating. Whether he was successful in his cheating or not, he had still finished the act of copying the answer. He wasn't caught by the hand in the process but may have been discovered afterwards)
Вася не знает математики, он получил "отлично", потому что списал на экзамене. (He managed to cheat successfully, that's how he got his A grade, though he doesn't know anything about Maths. Here we see the result of his successful cheating)
I am not even sure that the other native speakers would 100% agree with me. The last sentence, for instance, sounds perfectly natural with both aspects, though I would use perfective in that case.
Цитата:Да. "一" значит только один студент, т.е. единственное число. Поэтому я не понимаю, почему это "отдельные студенты".
有一个别考生
Actually I thought at first it was plural, too. We are used to "numeral+classifier+adjective+noun" structure, here the classifier is omitted (it
is omitted, right?) So the "一" doesn't look like a numeral, since it has got no classifier. To me, at least