We can never expect________bluer sky unl
题型：选择题
问题：
We can never expect________bluer sky unless we create________less polluted world.
A．a; a
B．a; the
C．the; a
D．the; the
We can never expect________bluer sky unless we create________less polluted world.
A．a; a
B．a; the
C．the; a
D．the; the