4 Look at these important dates in history and write positive or negative sentences with the past perfect.

Решение:

Задание требует составить предложения в Past Perfect, используя даты и события. Отмеченные галочкой (`✓`) предложения являются положительными, а крестиком (`✗`) — отрицательными.

• 1. 4500 BC - invent the wheel
  By 4500 BC they had invented the wheel. (✓) - Положительное предложение, действие произошло до указанного времени.
• 2. 1400 - start to print books
  By 1400 they had not started to print books. (✗) - Отрицательное предложение, действие не произошло до указанного времени.
• 3. 1805 - make the first battery
  By 1805 they had made the first battery. (✓) - Положительное предложение.
• 4. 1895 - discover X-rays
  By 1895 they had discovered X-rays. (✓) - Положительное предложение.
• 5. 1900 - fly for the first time
  By 1900 they had not flown for the first time. (✗) - Отрицательное предложение.
• 6. 1910 - discover penicillin
  By 1910 they had not discovered penicillin. (✗) - Отрицательное предложение.
• 7. 1932 - split the atom
  By 1932 they had split the atom. (✓) - Положительное предложение.

Ответ:

1. By 4500 BC they had invented the wheel.
2. By 1400 they had not started to print books.
3. By 1805 they had made the first battery.
4. By 1895 they had discovered X-rays.
5. By 1900 they had not flown for the first time.
6. By 1910 they had not discovered penicillin.
7. By 1932 they had split the atom.