Will someone please help me understand why the answer to the following problem (see below) is choice A instead of choice B?

Will someone please help me understand why the answer to the following problem (see below) is choice A instead of choice B?
Directions: Answer Questions 10 through 12 on the basis of the following information.
Four batches of lightbulbs purchased by the city from four different suppliers contained defective units in the following percentages:
Supplier