Answer:
What line is congruent to line CD? -- line AD (look at the tiny lines on each of them, that means they're congruent)
Which angle is congruent to angle DAB? -- DCB seems like the most appropriate option. Also, if this was an isosceles triangle, which has two congruent lines (as shown in the image) and two congruent angles, then it would be right to assume DAB and DCB are congruent.
What is the angle measure of angle ABD? -- 90° (the square means it is a right angle, or 90°)