Answer:
<em>Triangle ADC is a right triangle.</em>
Step-by-step explanation:
<u>Triangles Classification</u>
An <em>acute triangle</em> is a triangle with three acute angles or with less than 90° each.
An <em>obtuse triangle</em> has one obtuse angle or more than 90°.
A <em>right triangle</em> has one right angle of 90°
From the figure, we can see angle D is marked as a right angle (90°), thus triangle ADC is a right triangle.
To complete the answer, triangle ADB is obtuse (has an angle of 100°), and triangle ABD is acute.