用方框中所给单词的适当形式填空，使对话通顺、正确，每词仅用一次(每空一词)。

Human beings are always caring little about what they litter into water. To draw people's attention to the problem of water , an environmental group called Green kayak is doing something great. They allow travelers to the cities in Europe by boat for free, but the travellers have to pick up any rubbish they find along the waterway.

The group provides each traveller with a two-hour free boat tour, some tools, and also a life jacket. It's not necessary for travellers to be good at because they don't need to jump into water for the rubbish.

Since the program began in 2017, travellers have helped nearly 11,000kg rubbish, including plastic bags, bottles and even shoes.