What Does the Standard Deviation Tell You About the Variability

What does the standard deviation tell you about the variability in a data set

A)  When variability is high, the standard deviation is small. 
B)  The standard deviation does not reflect the variability in the data set. 
C)  A large standard deviation means that there is a great degree of variability in the data set. 
D)  As variability increases in a data set, the standard deviation becomes more variable as well.