The little circle is an invertor (a NOT gate). The logic gate with the inputs connect to a straight line is an AND gate. The logic gate with tinputs connected to a curved line is an OR gate. $A+B$ means $A$ OR $B$ , $A \cdot B$ means $A$ AND $B$ , and $\overline{A}$ means NOT $A$ . So, the upper input to the gate on the right is
$\begin{align*}\overline{\overline{A}+\overline{B}}\end{align*}$
and the lower input to the gate on the right is
$\begin{align*}\overline{C \cdot D}\end{align*}$
So, the output of the gate on the right is
$\begin{align*}\boxed{E = \overline{\overline{A}+\overline{B}} \cdot \overline{C \cdot D}}\end{align*}$
Therefore, answer (C) is correct.

Solution to 2008 Problem 48