The second problem is obviously gradual progress. First, divide the two teachers into two groups. There are two ways to divide them. In the second step, four students are divided into two groups, each with four points (c4 takes 2). Then multiply in two steps. The third problem is classification. The first category is that A gets one point, B gets two points, and the second category is that B gets one point and A gets two points. A point on line A and any two points on line B can form a plane, and they are the same plane. There are five points on A, so there are five kinds. There are 8 kinds in the second category, 5+8= 13. Fill in the blanks from A to C must go through D or B. Take adc as an example, there are four paths: arc-line, arc-arc, line-arc, line-line-line. The Abc line is symmetrical, so there are 8 lines.