Id number two. (2) The straight line AB 0 (zero) can extend indefinitely. Ray OA 1 can extend to the same line of defense indefinitely. AB 2 can't be expanded casually. (3) Two points determine a straight line. Three. (4) Connect AB, AC and BD(AB and AC should be prominent on both sides. DB point b should stand out. ) (6) straight line OA, OB, compared with point O, point A is outside the straight line EF. Lines A, B and C intersect in pairs at B, D, H. 1. Select (1) D (2) C.