Please help me with this math my teacher won’t help me

Which of the following statements is not true? a. parallel lines are lines in the same plane that never intersect. b. congruent figures have the same shape and same size angles and sides. c. similar figures must have the same shape and the same size. d. a rotation is when you turn a figure around a certain point.

Which property was used to simplify the expression? 3c+9 +4c=3c+4c+9

Whats are the trickiest steps to do when adding or subtracting rational expressions? how does knowledge of rational numbers u in adding and subtracting rational expressions?