用括号中所给动词的适当形式填空，使短文完整。
Alice and her sister want to make the
Earth a better place for people. They did a lot of things.
One day, while they {#blank#}1{#/blank#} (walk) in their hometown, they saw hundreds of
cigarette butts (烟头) on the ground. The cigarette butts made the town {#blank#}2{#/blank#} (look) so ugly that they decided to start a
group. They wanted to make people stop {#blank#}3{#/blank#} (drop) butts. The group {#blank#}4{#/blank#} (call) "No Butts About It" Many
people {#blank#}5{#/blank#} (start) to join their group after they heard
of their stories.
At the moment, they {#blank#}6{#/blank#} (try) to get cigarette companies to put an
ashtray (烟灰缸)
in each pack of cigarette. Today there are also other "No butts About It"
groups in America.
