What is the Boolean expression of the function implemented by the following combinational circuit?

a$.F=A{B}^{\text{'}}+(Co+D{)}^{\text{'}}$

b$.F=A{B}^{\text{'}}+(Co+D)$

$F=A{B}^{\text{'}}+Co+D$

$F=A{B}^{\text{'}}+(C+D{)}^{\text{'}}$

$F=(A{B}^{\text{'}}+(Co+D){)}^{\text{'}}$

$9C$

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