【简答题】
A、K<sub>1sub>+K<sub>2sub> B、K<sub>1sub>-K<sub>2sub> C、K<sub>1sub>·K<sub>2sub> D、K<sub>1sub>/K<sub>2sub>
A、K<sub>1sub>+K<sub>2sub> B、K<sub>1sub>-K<sub>2sub> C、K<sub>1sub>·K<sub>2sub> D、K<sub>1sub>/K<sub>2sub>