The Lower Limit,L,and the Upper Limit,H,are

The lower limit,L,and the upper limit,H,are:

A) just outside points but no transaction are made.
B) the points at which Z - L securities are sold and H - Z securities are bought.
C) the points are which Z - L securities are bought and H - Z securities are sold.
D) the points at which Z -L is transacted but any value above Z is held.
E) None of the above.