Answer:
C
Step-by-step explanation:
Since angles x and y lie on a single straight line,
∠x +∠y= 180° (adj. ∠s on a str. line)
Given that ∠x= 42°,
42° +∠y= 180°
∠y= 180° -42° (-42° on both sides)
∠y= 138° (simplify)
Thus, option C is correct.
