听力原文：Antram Incorporated is instituting a new recycling program. Our first step is to

place sets of recycling bins around our facilities. A set is made up of three separate recycling bins that will be dedicated to the collection of aluminum cans, plastic bottles, and newspaper and other paper. There will be four sets altogether. One will be placed in the first floor operations break room, one will be placed in the second floor administration break room, and two will be placed in the cafeteria. Depending on the overall success of this program, additional recycling collection points may be added. Your participation in and support for the program is greatly appreciated.

How many total sets of recycling bins will be placed in the building？

A．3

B．4

C．5

D．6