请用英语回答：在一个很小的（tiny）荒岛上的四样必备品.并说明原因

First,I would bring a water treatment device because I need to purify the water nearby in order to survive.Second,I would bring a knife to guide myself from animal's attack.Then,food seeds are needed because I could plant them and get the necessary food from it.What's more,the seeds could be collected after they come to flower.Last,I would bring a camera because I want to take pictures for memories.

water food computer