Answer:
C. 4.5 cm
Explanation:
As you can see on the triangles at the picture, you can see that each side there are lines which represent congruency to other triangle.
At the side where there is I, the measure is 2.5 cm.
At the side where there is II, the measure is 3.5 cm.
At the side where there is III, the measure is 4.5 cm.
On the III where the Question Mark sign is located, the value is 4.5 cm. Therefore, the missing value is 4.5 cm.
