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.