#### Answer

$B; C
\\A; C$

#### Work Step by Step

Exercise 89 shows that in a line, the distance from the 1st point to the 4th point is equal to the sum of the distance between the first two points and the distance between the 2nd and the 4th point.
Thus, if points A, B, and C lie on the same line in that order, the distance between A and C is equal to the sum of the distance between A and B and the distance between B and C.
Therefore, the missing expressions in the given statement, in order, are:
B; C
A; C