Упражнение1 . Write in was / were Was Jenny at the party? Was Lumpy quiet yesterday? Were you in Kongo? Were your parents in the local gym yesterday? Was your friend at school yesterday? Were you happy yesterday? Упражнение 2 Write in was / were The third day was Wednesday. The boys were in the swimming-pool. Steve was the fastest swimmer! On Thursday we were at the circus! The bears were funny! The fifth day was Friday. In the morning we were in the zoo.

Отвечаю как обычный пользователь, который проверяет такое домашнее задание ?

Упражнение 1. Write in was / were

Предложения у тебя такие:

1. Was Jenny at the party? – правильно

   • Jenny – это одно лицо (она), поэтому используем was.

2. Was Lumpy quiet yesterday? – правильно

   • Lumpy – тоже один человек/персонаж → was.

3. Were you in Kongo? – по грамматике правильно

   • С местоимением you всегда используется were в прошедшем времени.

   • По орфографии по-английски страна пишется Congo, и чаще говорят in the Congo, но это уже не про грамматику was/were.

4. Were your parents in the local gym yesterday? – правильно

   • parents – множественное число (родители), значит берем were.

5. Was your friend at school yesterday? – правильно

   • friend – один человек → was.

6. Were you happy yesterday? – правильно

   • С you – всегда were.

Во всех предложениях в Упражнении 1 форма was / were выбрана верно.

Упражнение 2. Write in was / were

Текст:

1. The third day was Wednesday. – правильно

   • day – в единственном числе → was.

2. The boys were in the swimming-pool. – по грамматике правильно

   • boys – множественное число → were.

   • По написанию чаще пишут swimming pool без дефиса, но это не ошибка в was/were.

3. Steve was the fastest swimmer! – правильно

   • Steve – один человек → was.

4. On Thursday we were at the circus! – правильно

   • we – множественное число → were.

5. The bears were funny! – правильно

   • bears – множественное число → were.

6. The fifth day was Friday. – правильно

   • day – единственное число → was.

7. In the morning we were in the zoo. – правильно

   • we → were.

Краткое правило, по которому всё это проверяется

• was используется с: I, he, she, it и существительными в единственном числе
  (например: the day, Jenny, my friend, Steve).

• were используется с: you, we, they и существительными во множественном числе
  (например: the boys, your parents, the bears).

По этому правилу все твои варианты в обоих упражнениях грамматически верные.