need somce clarification

uzhany

I am new at the BBS stuff, so excuse my stupid question,  I have see "c" in the math explanation, what does it mean?[em01]

christinecc

A--only I, not II
B--only II,not I
C means that both I and II can get the result,but any one of them is not sufficient.
D means each can get the result.
E-neither