1. The problem asks which segment is congruent to the given segment of length 18 cm. 2. Congruent segments have the same length. 3. The given segment length is 18 cm. 4. We compare the lengths of other segments: 36 cm and 9 cm. 5. Since 36 cm and 9 cm are not equal to 18 cm, they are not congruent. 6. Therefore, the segment labeled 18 cm is congruent to the given segment. Final answer: The segment of length 18 cm is congruent to the given segment.