To determine the decimal form of the fraction \(-\frac{5}{6}\), we can perform the division of 5 by 6.
When you divide 5 by 6, you get:
\[ 5 \div 6 = 0.8333\ldots \]
The decimal representation is \(0.8333...\), which means that the digit "3" repeats indefinitely.
From the choices provided, the correct answer is:
C. It is a repeating decimal.