中国学生最常犯的错误之一就是用“it”这个代词返指之前的篇章。“it”在英文中有这样几种常见用法： 指代之前的一个单数名词（非人） 作为形式主语 指代一个that引导的名词性从句 指代一个 动词不定式
My best friend is using an irrational and ineffective learning model, which let her stumble from time to time, and she is completely unaware of the negative impact of her choice. It’s hard for me to watch this.
这句话里面，this指的究竟是什么呢？其实，换成一个名词就可能非常清楚了： My best friend is using an irrational land ineffective learning model, which let her stumble from time to time, and she is completely unaware of the negative impact of her choice. It’s hard for me to watch her suffer.
nouns which refer back to texts, classing them as types of verbal action:
account, accusation, acknowledgement, admission, advice, allegation, announcement, answer, apology, appeal, argument, assertion, assurance, boast, charge, claim, comment, complaint, compliment, concession, condemnation, confession, contention, correction, criticism, declaration, defence, definition, demand, denial, denunciation, description, digression, disclosure, discussion, endorsement, excuse, explanation, exposition, gossip, information, judgement, lie, message, narrative, objection, observation, plea, point, prediction, promise, pronouncement, prophecy, proposal, proposition, protest, question, reference, refusal, remark, reminder, reply, report, request, response, retort, revelation, rumour, statement, stipulation, story, suggestion, summary, tale, threat, verdict, warning
nouns which refer to ideas and show your feelings about the ideas:
analysis, assessment, assumption, attitude, belief, conclusion, conjecture, concept, deduction, delusion, diagnosis, doctrine, doubt, estimate, evaluation, fear, finding, guess, hope, idea, illusion, inference, insight, interpretation, misinterpretation, notion, opinion, picture, plan, position, reasoning, supposition, theory, thinking, view, viewpoint, vision, wish
nouns which refer to events and are neutral:
act, action, affair, aspect, case, circumstances, context, development, effect, episode, event, experience, fact, factor, feature, incident, issue, matter, method, move, phenomenon, position, possibility, practice, process, reason, respect, result, situation, state, state of affairs, subject, system, thing, topic, way
nouns which refer to events and show your feelings about them:
achievement, advantage, answer, crisis, difficulty, disadvantage, disaster, exploit, feat, nightmare, plight, predicament, problem, solution, tragedy
nouns used to refer to a piece of writing:
chapter, example, excerpt, extract, instalment, item, letter, paragraph, passage, phrase, quotation, section, sentence, statement, summary, table, text, words
– quoted from Egnlish Grammar, Cobuild HarperCollins Publishers