In this question

We use BODMAS and decimal Rule,

$\begin{array}{l}\text{ 999 + 111}\times \text{0.5}\\ =\text{999+111}\times \frac{1}{2}[\because 0.5=\frac{1}{2}]\\ =\text{999 + 55.50}\\ \text{ = 1054.50}\end{array}$

Hence, Option C is correct.