The correct option is C.
When a dog is afraid, its ears are usually pinned back to the head. A dog showing aggression will pulled its ear up and forward.
Other signs that a dog shows when it is afraid include: lowering of the head, wrinkling of the nose, curled lips that show many teeth, tucked tail, panting, etc.
Signs show by an aggressive dog include: head held high, curled lips only show the front teeth, tail is upright and stiff, no panting, etc.
Answer:
The modern medical era began when an absent-minded British scientist named Alexander Fleming returned from vacation to find that one of the petri dishes he forgot to put away was covered in a bacteria-killing mold. He had discovered penicillin, the world's first antibiotic.
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Its A. it prevents sperm from reaching the egg and fertilizing it.