When Using Timechart , How Many Fields Can Be Listed

Multiple Choice

When using timechart , how many fields can be listed after a by clause?

A) 0, because timechart doesn't support using a by clause.
B) 1, because _time is already implied as the x-axis.
C) 2, because one field would represent the x-axis and the other would represent the y-axis.
D) There is no limit specific to timechart.