Even a very small treatment effect can be statistically sign

Even a very small treatment effect can be statistically significant if
A) the sample size is big and the sample variance is small
B) the sample size and the sample variance are both big
C) the sample size is small and the sample variance is big

Solution

Even a very small treatment effect can be statistically significant if
A) the sample size is big and the sample variance is small
B) the sample size and the sample variance are both big
C) the sample size is small and the sample variance is big

Note:

Large sample size and small variance leads to small standard error.

Smaller the standard error more often the significant results.