To determine the measure of segment \( \overline{AC} \), we note the following:
- The segment \( \overline{AB} \) measures 22.3 millimeters.
- Point \( B \) is the midpoint between points \( A \) and \( C \).
Since \( B \) is the midpoint, the entire length of segment \( \overline{AC} \) is twice the length of segment \( \overline{AB} \). Therefore, we can calculate the measure of \( \overline{AC} \) as follows:
\[ \text{Length of } \overline{AC} = 2 \times \text{Length of } \overline{AB} = 2 \times 22.3 \text{ mm} = 44.6 \text{ mm}. \]
Thus, the measure of \( \overline{AC} \) is 44.6 millimeters.
The correct response would be:
- The measure of \( \overline{AC} \) is 44.6 millimeters.