When either selector or pushbutton switches are drawn with more than one set of contacts (indicating more than one rung of switching in the ladder diagram — a stacked switch), a __________ is used to indicate all the switching contacts that are interconnected with mechanical linkage to activate (either open or close) simultaneously with the movement of a single operator.
A) broken line
B) curved line
C) solid line
D) bold line
Share your understanding of this question with the correct explanation.