My heart is about as big as my fist. Each side of it works. The right side receives blood from the rest of my body. It pumps the blood to my lungs. In my lungs, blood takes oxygen from the air. The…
should go. Click! The minute you turn on a lamp or a radio, something happens—a light bulb glows or sounds come out. But electricity doesn’t jump into the lamp or the radio. It flows through…
Billions of tiny plants and animals drift in huge groups in the sea. These creatures are so small that most of them can be seen only with a microscope. The sea is filled with many different kinds…
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