1.a2.b3.c4. 150 5。 (1). Because O is a point on the straight line AB, ∠ AOD+∠ BOD = 180 and ∠AOC =∞.

sketch

1.A2.B3.B4. 180 5。 ∠ B ∠ BDE 6。 Omit 7.

1.D 2。 B 3。 B 4。 B 5。 Northeast China 45 26. ②4, left 7. After translation, the distance A walked was the discounted length of AMO, so ants A and B returned to the cave at the same time.

Let's not talk about that. Ha, do it yourself.