Помогите пожалуйста ответить на тест:
1) There is____acid in ordinary rain.
a)always
b)no
c)strong
2) Acid rain_____.
a)appeared in the 20-the century
b)has always existed in nature
c)is the result of industrial development.
3)______is the cause of acid rain .
a)burning coal and oil
b)the wind
c)water in the air