What is the structure labeled a? the options are in the picture !

a axis of a graph is a color or shade so we can all go outside and have a party so we can eat   some grilled cheese sammiches and broccoli and have some ugly fun times

i don't know why i put this, i know its not the i was just bored : p

delete this answer while you can

the answer is :

if you listed your answers right then i believe your answer is b.