us.
It can be inferred from the last paragraph that scientists().
A.are puzzled by the mystery of forest pollution
B.feel relieved by the use of unleaded gasoline
C.still consider lead pollution a problem
D.lack sufficient means to combat lead pollution
_ of her smile. When you're not looking at her, she seems to be smiling; when you look at her, she stops.
A、barrier
B、misfortune
C、prospect
D、mystery
______ it will do us harm or good remains to be seen.
A.Whether
B.If
C.As
D.All
A.seems to be
B.looks to be
C.remains
The villagers were surprised to see the() of an aeroplane near the lake.
A.remains
B.remain
C. thing
D.matter
In spite of high divorce rate the of marriage remains popular.
A.habit
B.state
C.practiced
D.institution