Complete these sentences with the correct form of the verb in brackets. 1 Prehistoric paintings (appear) in caves thousands of years ago. 2 Graffiti (be) a problem since aerosols appeared. 3 The artists (finish) their mural a moment ago. 4 Last week, I (go) to the museum to see an exhibition of graffiti art. 5 They (not paint) the wall yet. 6 He (become) an artist in 1990. 7 They (cover) a wall with graffiti during the night.

Краткое пояснение:

1. Appeared (Past Simple), так как действие произошло в прошлом.
2. Has been (Present Perfect), так как проблема существует с момента появления аэрозолей и до сих пор.
3. Have finished (Present Perfect), так как действие завершилось недавно, и виден его результат.
4. Went (Past Simple), так как действие произошло в прошлом (на прошлой неделе).
5. Have not painted (Present Perfect), так как действие не завершено к настоящему моменту.
6. Became (Past Simple), так как действие произошло в конкретный момент в прошлом (в 1990 году).
7. Covered (Past Simple), так как действие произошло в прошлом (ночью).

Ответ:

• Prehistoric paintings appeared (appear) in caves thousands of years ago.
• Graffiti has been (be) a problem since aerosols appeared.
• The artists have finished (finish) their mural a moment ago.
• Last week, I went (go) to the museum to see an exhibition of graffiti art.
• They have not painted (not paint) the wall yet.
• He became (become) an artist in 1990.
• They covered (cover) a wall with graffiti during the night.