A triangle has an [a_ _t_] angle

The averageEarth [d_ _m_ _ _ _] is about 12 742 km

Air pollution from the burning of fossil fuels is the major cause of acid [r_ _n]

Greenhouse [g_ _e_] are components of the atmosphere...

Over past 250 years [c_ _b_ _] dioxide level have increased.

Greenhouse gases come from [n _ _ _ _ _l] sources and human activity.

When the acid builds up in [ri_ _ _ _] and streams, it can kill fish

What is the [c_ _ _e] of global worming?