What does social security fit and with b mean

Many of the students who rely on the constructor's certificate will see the requirement for the only social security plus the need for a B certificate when they are looking for a company to rely on. A person around the license will be completely eliminated, the national social security network, each person will have a separate social security account, a person has more than one area of the builder's credentials will be social security system to find out, the builder's credentials to rely on must be with their own payment of social security unity. b certificate is a construction safety officer three categories (known as the safety of the "three types of personnel"). The B license is one of the three types of construction safety personnel (called safety "three types of personnel"). Three types of personnel refers to the main person in charge of building construction enterprises, project managers and full-time production safety management personnel, ABC each certificate is just a different scope of work and responsibility positioning, and there is no difference between high and low.