Упражнение 1. В данном упражнении вы должны выбрать правильную форму глагола, исходя из контекста представленных предложений.
1)I discovered that someone … the last apple when I opened my refrigerator.
• had eaten
• has eaten
2)Christina failed the exam because … .
• hadn’t studied
• hasn’t studied
3)Peter … with everyone in the party by the end of the evening.
• had talked
• has talked
4)I…Russian food until my journey to Russia last year.
• has tasted
• had tasted
5)They … their keys in the car that’s why they couldn’t drive away.
• have locked
• had locked
6)Students … new Chemistry teacher yet.
• hadn’t met
• haven’t met
7)Don’t pour your coffee on the flour – my sister … the flat.
• had just cleaned
• has just cleaned
8)Jane is working late again? She … overtime every week this month.
• has worked
• had worked
9)Dane … Russian food.
• has never had
• had never had
10)We had a great time on our meeting last night but my friends … me since.
• hadn’t called
• haven’t called.

1 had eaten

2 hadn't studied

3 had talked

4 had tasted

5 had locked

6 haven't met

7 has just cleaned

8 has worked

9 has never had

10 haven't called

1. Had eaten - действие закончено

2. Hadn't studied - действие закончено

3. Had talked - действие закончено

4. Hadn't tasted - действие закончено (в предложенных вариантах правильного по смыслу нет)

5. Have locked - действие не закончено

6. Haven't met - действие не закончено

7. Has just cleaned - действие только завершилось

8. Has worked - действие не закончено

9. Has never had - действие не закончено

10. Haven't called - действие не закончено

Предлагаю смотреть на все перфекты так:

Глагол have - иметь, давай будем переводить его дословно.

Например, I haven't called you --> я не имею звонившей тебе т.е я тебе все еще не позвонила

А вот другой пример, I hadn't called you untill it was too late - я не имела звонившей тебе пока не было слишком поздно т.е Я тебе не позвонила пока не стало слишком поздно.

Заметим, что в первом примере действие имеет отношение к настоящему, а во втором идет повествование о

Вот такой очень краткий инсайт в процессе понимания этой грамматики, если конечно же интересно