What is the missing step in this proof? A.
Statement: 24 25, and 21 23.
Reason: Alternate Interior Angles Theorem
B.
Statement: DÈ is parallel to AC.
Reason: AB is a transversal cutting De and AC.
C.
Statement: 2124, and 23 25.
Reason: Alternate Interior Angles Theorem
D.
Statement: 2124, and 23 25.
Reason: 21 and 24, and 23 and 25 are pairs of supplementary angles.

b

Step-by-step explanation:

because BC are parallel to AC

second option

step-by-step explanation:

the measures of a triangle equal 180. use that to find x.

2x+3x+4x=180

9x=180

9x/9=180/9

x=20

now you know x, you know angle a is 40°, angle b is 60°, angle c is 80°.

because angle a is 40°, the first option doesn't work.

because angle b is 60°, the second option does work.

when you add angle a and b, you get 100°. complementary means it equals 90°, so the third option doesn't work.

when you add angle a and c, you get 120°, which is not 100.