A、<span style=";font-family:宋体;font-size:14px">关系运算</span></p><p></p>
B、<span style=";font-family:宋体;font-size:14px">谓词演算 </span></p><p></p>
C、<span style=";font-family:宋体;font-size:14px">集合运算</span></p><p></p>
D、<span style=";font-family:宋体;font-size:14px">代数运算</span></p><p></p>