Can someone explain greatest common factor/lowest common multiple to me, in a way that i can understand? because i'm not getting what's being said or how to solve the equation.

my textbook says this:

"the greatest common factor (gcf) of two natural numbers x and y is the largest natural number that is a factor of both x and y, while the least common multiple (lcm) of x and y is the smallest natural number that is a multiple of both x and y.

for instance, the gcf of 18 and 24 is 6, while the lcm is 72. 1. which of the following statements is false? "

(a) the greatest common factor of 5 and 20 is 5.

(b) 100 is a multiple of 5.

(c) 40 divides 120.

(d) the least common multiple of 10 and 20 is 40.

(e) 5 is a factor or 125.