在一定温度下，将2mol SO₂和1mol O₂充入一定容积的密闭容器中，在催化剂作用下发生如下反应：2SO₂（g）+O₂（g）⇌2SO₃（g）；△H=-197kJ•mol^-1，当达到化学平衡时，下列说法中正确的是（　　）

A．生成SO₃2mol

B．SO₂和SO₃共2mol

C．放出197kJ热量

D．含氧原子共8mol

In the following essay, each blank has four choices. Choose the most suitable one from the four choices and write down in the answer sheet.

A socket is basically an end point of a communication link between two applications. Sockets that extend over a network connect two or more applications running on (31) computers attached to the net-work. A socket (32) two addresses: (33) . Sockets provide a (34) communication channel between one or more systems. There are (35) sockets separately using TCP and UDP.

（34）是（）

A.full-duplex

B.half-duplex

C.simplex

D.complex