Right Answer is: B
In the diagram shown below, triangle ABC is right angled triangle (Angle subtended by a diameter/semicircle on any point of circle is 90 degrees). So ∠ACB= 90, ∠BAC = 24°
Then, ∠ABC = 180 – (90+24) = 66
As given that ABCD is a trapezium so, CD must be parallel to AB.
Hence, ∠DCA = ∠BAC = 24
Using cyclic quadrilateral theorem, sum of opposite angles of cyclic quadrilateral is 180.
So, ∠ADC + ∠ABC = 180
∠ADC + 66 = 180
∠ADC = 114
In triangle ADC, sum of angles ∠CAD + ∠ACD + ∠ADC = 180
∠CAD + 24 + 114 = 180
CAD = 180-138= 42
Hence, option B is the correct answer.