题目内容：
请在（4）处填写正确答案。
A．They can watch them develop inside their eggs and feel the skin of the older swimmers. B．A shocking 100 million sharks are killed every year around the world by humans.
C．In fact, 94 percent of the world's 400 species are harmless to humans.
D．It is a worrying situation and some areas have put measures in place to protect these special fish.
E．And to make this point clear, the museum has set up a special touching pool for children.
F．More than half of the sharks caught are smaller than 1 meter long.
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