Which of the Following Is an Advantage of Using Single

Which of the following is an advantage of using single sourcing?

A) Suppliers are more likely to remain cost-competitive.
B) Buyers are less reliant on one firm to deliver the needed goods without interruption.
C) The buyer and seller agree to be each other's customers.
D) Consistency of quality of materials input into the product process is greater.
E) Buyers have other suppliers to fall back on if one supplier fails.