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Natural gas
explanation:
solar power, coal, and petroleum are used to power things (i.e. produce electricity)
D) Robert Hooke first discovered cells when observing cork under the microscope.
The correct option is A.
The serosa refers to the outermost layer of loose connective tissues which is often covered by mucus and which contains blood vessels. In the gastrol intestinal tract, the serosa refers to the outermost layer of the wall of the GI tract. One major function of serosa is to reduce friction from muscle movement.
