总口令:圈时间词 → 判点/段 → 选公式。
判断「点」还是「段」: 点(具体时间 = last night / yesterday / at 8pm)→ 用一般过去 performed 段到现在(so far / since / for...now)→ 用现在完成 has/have done 段到过去某点(by the time / before...)→ 用过去完成 had done 此刻正在(right now / at this moment)→ 用现在进行 is/are doing 过去某刻正在(when... / while...)→ 用过去进行 was/were doing 持续到现在(for X months now)→ 用现在完成进行 has been doing 规律/习惯(every morning / always)→ 用一般现在 performs