Given that,
Standard deviation = s = 5.5
Sample size = n = 64
standard error = x = ?
If we are given the standard deviation and sample size, the error can be calculated using the following formula.
![x\text{ = }\frac{s}{\sqrt[]{n}}](https://img.qammunity.org/2023/formulas/mathematics/college/6dkkxg3qidxwgf8w26t6o9upcs0wlzwj9y.png)
By putting the values in the formula, we get
![x\text{ = }\frac{5.5}{\sqrt[]{64}}](https://img.qammunity.org/2023/formulas/mathematics/college/ag7u33a7lelnbphk3440zmax40nbpk4rrm.png)
or
x = 5.5/8
x = 0.6875
As we have to round the answer to two decimal places, the final answer would 0.69.
Hence, option C is correct.