We need to find the fraction of the test questions that Rita answered incorrectly.
We know that Rita correctly answered 9 questions. Since the test had 10 questions, Rita answered incorrectly 1 question.
So, Rita answered incorrectly 1 out of 10 questions. And we represent this fraction by writing the number of correct questions over the total number of questions::
![(1)/(10)](https://img.qammunity.org/2023/formulas/mathematics/high-school/tpj7kspe5lr8a2k97kwvye2ux8z9j8frm6.png)
Therefore, the answer is option C.