Answer:
option:A is correct.
Step-by-step explanation:
Since g,h and l are parallel lines and a line intersect these 3 lines making angles 1,2,....12.
By looking at the figure we could say that
∠2=∠6 since they are pair of corresponding angles.
Hence ∠6=129°
similarly ∠6=∠10 as they are also pair of corresponding angles.
Hence ∠10=129°
Now we know that ∠10+∠12=180° .
(since both the angles lie on a straight line)
129°+∠12=180°
∠12=180°-129°
∠12=51°
Hence option A is correct.(i.e. measure of ∠12 is 51°)