Даю 50 балів. Допоможіть.

Відповідь:

Lee has been surfing the Net for four hours.

Ian and Henry has been watching TV for twenty minutes

Ace has been sleeping since 6 o'clock

Tom has been looking after little brother since this morning.

Пояснення: Можуть бути помилки, адже сама не зрозуміла трохи правило.