3. His friends / at the circus last Sunday (X)

Solution:

Fill in the blanks with 'was' or 'were'. The sentences provided are examples of how to use these verbs correctly. The symbol '(X)' indicates a negative statement, and '(v)' indicates a positive statement.

1. His friends were at the circus last Sunday. (Friends is plural, so 'were' is used. The sentence is positive, indicated by the absence of 'X' or '(v)' suggesting it should be positive or is a statement to be completed. Assuming it is a statement to be completed based on the context of filling blanks, and given the structure and expectation of grammar exercises, it's most likely intended as a positive statement.)
2. Sveta was at the party last night. (Sveta is singular, so 'was' is used. The '(X)' likely indicates that a negative statement should be formed if completing the sentence, but the prompt structure suggests filling in the verb. Assuming the task is to fill in the correct form of 'to be', 'was' is the correct singular form. If the task was to negate, it would be 'wasn't'.)
3. Larisa and Olga were at the café 2 days ago. (Larisa and Olga are plural, so 'were' is used. The '(v)' indicates a positive statement.)

Answer: were, was, were.