The inscribed angle is 42 degree.
To determine the measure arc AC,
Use the formula
[tex]m\angle ABC=\frac{1}{2}m\hat{AC}[/tex][tex]m\hat{AC}=2\times42^{\circ}=84^{\circ}[/tex]
Hence the measurement of arc AC is 84 degree .
Hence the correct option is d.
