阅读下面短文，在空白处填1个适当的单词或括号内单词的正确形式(请将答案写在题后横线上)。
Clothes are
traditionally made of natural materials, such {#blank#}1{#/blank#} cotton, leather and wool. They are all from plants or animals,
but that doesn't mean they are {#blank#}2{#/blank#} (friend) to the earth. For example, farmers sometimes have {#blank#}3{#/blank#}
use a lot of chemicals to grow cotton plants.
Scientists now {#blank#}4{#/blank#} (look for) new ways to make clothing materials. They hope the new
materials are both comfortable and good for the earth. So far, scientists{#blank#}5{#/blank#} (work) out how to make materials out of corn husks (壳), chicken feathers and rice straws. I think
more and more people will like to buy these kinds of clothes.
