用所给词的适当形式填空①When I saw her, she was busy {#blank#}1{#/blank#} (write) a letter.
②The environment {#blank#}2{#/blank#} (pollute) is becoming more and more serious.
③You {#blank#}3{#/blank#} ever {#blank#}4{#/blank#} (throw) things about, haven't you?
④I was {#blank#}5{#/blank#} (surprise) to find hardly anyone in the zoo.
⑤The workers are all against the boss's idea {#blank#}6{#/blank#} (strong).
