4) Vicki cleaned up the wood ...

Решение:

• В тексте сказано: "Suddenly she had an idea. 'We must clean up the place,' she thought. At home she phoned four of her schoolfriends. They all agreed to help her. It was hard work but soon they put all the rubbish into big bags and took it away."
• Это означает, что Вики обратилась за помощью к своим подругам (schoolfriends) и вместе с ними убрала мусор.
• Таким образом, она убрала лес b) with the help of her girlfriends.

Ответ: b) with the help of her girlfriends