If Some Fact of an Experiment Results in a Smaller

If some fact of an experiment results in a smaller standard error of the difference between two means than otherwise, this is

A) undesirable, because it will make it less likely to claim a difference when one exists
B) undesirable, because it makes it more likely to claim no difference when there is a difference
C) desirable, because it makes it more likely to claim a difference when one exists
D) desirable, because it makes it less likely to claim a difference when there is none