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#39467

lines

angles

geometry

easy

30 sec

In the figure shown, line $ℓ$ intersects lines $m$ and $n$ . Let the upper-left interior angle be $A$ , the upper-right interior angle be $B$ , the lower-left interior angle be $C$ , and the lower-right interior angle be $D$ . Which of the following conditions is sufficient to prove that line $m$ is parallel to line $n$ ?

A.

The sum of angle $A$ and angle $D$ is $18 0^{\circ}$ .

B.

Angle $A$ is equal to angle $D$ .

C.

The sum of angle $A$ and angle $C$ is $9 0^{\circ}$ .

D.

Angle $D$ is equal to angle $C$ .