2.∵ad‖bc∴∠a+∠b= 180≈a = 60∠b = 120

You can't get ∠D without measurement.

3. (1) ∠ 2 =110 (two straight lines are parallel with equal internal angles).

(2) ∠ 3 = 1 10 (two straight lines are parallel with the same included angle)

(3) ∠ 4 = 70 (two parallel lines are complementary angles of each other)

4.∫a‖b∴∠2 =∠ 1 = 80 (two straight lines are parallel with the same offset angle) ∠ 5+∠ 3 = 180 (two straight lines are parallel with the same inside)

5.60 Because two straight lines are parallel and complementary.

6. The internal dislocation angles are equal and the two straight lines are parallel.

Two straight lines are parallel and have equal internal angles.

7.( 1)C(2)C