A couple decides to have 4 children. If they succeed in having 4 children and each child is equally likely to be a boy or a girl, what is the probability that they will have exactly 2 girls and 2 boys?
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A$$\frac{3}{8}$$
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B$$\frac{1}{4}$$
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C$$\frac{3}{16}$$
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D$$\frac{1}{8}$$
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E$$\frac{1}{16}$$