What can be said about a set of data with a standard deviation of​ 0?

​(This is a reading assessment question. Be certain of your answer because you only get one attempt on this​ question.)

Choose the correct answer below.

1. All the observations are 0.
2. For every positive​ value, there is a corresponding negative value​ (as in 4 and −​4; 6 and −​6).
3. All the observations are the same value.