如何判断一个Socket对象当前是否处于连接状态:()。
A. boolean isConnected=socket.isConnected() && socket.isBound();
B. boolean isConnected=socket.isConnected() && !socket.isClosed();
C. boolean isConnected=socket.isConnected() && !socket.isBound();
D. boolean isConnected=socket.isConnected() ;