Solution -





Firstly, we are marking the triangle as ABC ( see the image )

Now, <a°= <BAC because vertically opposite angles are equal. (see the image)

Therefore, <ABC+ <BAC+ <ACB =180° (Angles in a triangle sum to 180°)

=> <b°+ <a°+ <ACB=180°

=> <a°+ <b° = 180° - <ACB (This is Quantity B)

Now, let us look at Quantity A,

We know that a straight line has an angle of 180°

Hence, <c°= 180° - <ACB (This is Quantity A)

So, Quantity A = Quantity B

The correct answer is Option C.