in the city."
"That would be a little difficult,
Kareem," replied his grandfather,
"because car exhaust, the smoke
from chimneys, especially in win-
ter, and the scarcity of trees and
plants prevent the air in the city
from being clean."
Kareem pondered a little: "I un-
derstand the smoke, but I don't quite
understand what plants have to do with it.
Trees are meant to bear fruit and make the city
beautiful, aren't they?"
"Yes," answered Grandpa Hassan, "trees do all that; but prob-
ably more importantly, they also clean the air. Plants breathe in just
the opposite way to other living things. Human beings and animals
take oxygen from the air, and after using it in their bodies, they
breathe out the used air as carbon dioxide. But plants do the op-
posite: they take in carbon dioxide and give off oxygen, which is
how they clean the air. There are other wondrous qualities that
plants have, Kareem, and it is Allah, the All-Wise, Who has
created all of them. If you would like, I will tell you what I
know about plants."
"Yes, please, Grandpa; I'm all ears!" shouted
Kareem excitedly.
Grandpa Hassan took a deep breath and
began, "Plants breathe in a process called
photosynthesis."
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