In this triangle, which of the following is true?A. The measure of x is 55° and a = 5.74.B. The measure of x is 35º and a = 5.74.WC. The measure of xis 35º and a = 8.19.D. The measure of xis 55° and a = 11.47.

The given figure is a right triangle, and the sum of two acute angles other than the 90 degree is always 90.
So the equation will be :
[tex]x+55=90[/tex]Solve for the value of x :
x = 90 - 55
x = 35
Use sine function in finding the value of a :
Note that :
[tex]\sin \alpha=\frac{\text{ opposite}}{\text{ hypotenuse}}[/tex]Where alpha is the angle equal to 55,
"a" is the opposite side
and
10 is the hypotenuse
[tex]\begin{gathered} \sin 55=\frac{a}{10} \\ a=10\sin 55 \\ a=8.19 \end{gathered}[/tex]Therefore, the correct answer is Option C.