Which words or phrases in this excerpt from "the red wheelbarrow" by william carlos williams show that the wheelbarrow is an essential part of life on a farm?

The correct answer for the question that is being presented above is this one: "a. so much depends upon." The words or phrases in this excerpt from "The Red Wheelbarrow" by William Carlos Williams show that the wheelbarrow is an essential part of life on a farm is that a. so much depends upon 

Here are the following choices:
so much depends 
upon 
a red wheel 
barrow 
glazed with rain 
water 
beside the white 
chickens. 

a. so much depends upon 
b. barrow 
c. rain water 
d. beside the white chickens.