Beijing is introducing mandatory(强制性的)garbage sorting rules in public spaces such as "schools, hospitals, business office buildings, and tourist sites." The mandatory garbage sorting rules would gradually cover the entire city said Beijing Deputy Mayor Zhang Jiaming. By the end of 2019, 60 percent of the city will have garbage sorting areas. Residential areas will have garbage bins equipped with scales and waste identification devices.“We will set up a mechanism that garbage trucks can refuse to transfer trash if it is not classified,” Zhang said. （找出中心句）