英语听力精选进阶版 13925（在线收听）

American superweeds

Vocabulary

harvesting

gathering

herbicides

toxic chemicals used to kill weeds

to stem

to stop or restrict

resistance

ability of an organism to protect itself

seeking

applying for

a component

a part of

defoliant

chemical that removes the leaves from trees and plants

extensively

over a wide area

get the go-ahead

be allowed to start

incorporate

include