Nozomi constructed a copy of AB¯¯¯¯¯¯¯¯ by using point B as an endpoint of the copy of AB¯¯¯¯¯¯¯¯ and placing point C, as seen in the image. If the measure of AB¯¯¯¯¯¯¯¯ is 22.3 millimeters, what is the measure of AC¯¯¯¯¯¯¯¯?

To determine the measure of \( \overline{AC} \), we first need to understand how Nozomi constructed \( \overline{AC} \). It was mentioned that point \( B \) is used as an endpoint for the copy of \( \overline{AB} \), meaning that \( \overline{AC} \) extends from point \( A \) to point \( C \) with \( C \) being the new point created by this operation.

Since \( \overline{AB} \) has a measure of 22.3 millimeters, and \( \overline{AC} \) is formed by extending this segment continuously using \( B \) as a new endpoint, we can deduce the length of \( \overline{AC} \).

Assuming \( \overline{AC} \) is formed by placing another segment equal to \( \overline{AB} \) after point \( B \), the total length would be:

\[
AC = AB + BC
\]

Here, since \( BC \) is also a copy of \( \overline{AB} \), then:

\[
BC = 22.3 \text{ millimeters}
\]

Thus, the total length would be:

\[
AC = 22.3 + 22.3 = 44.6 \text{ millimeters}
\]

Therefore, the measure of \( \overline{AC} \) is **44.6 millimeters**.

The correct response is:
- The measure of \( \overline{AC} \) is 44.6 millimeters.