______________[A] incredible [B] spontaneous [C]inevitable [D] gradual

有两个关系R（A，B，C)和S（B，C，D)，则R÷S结果的属性个数是__________．

— Susan ,what do you think of my plan？— _______________A、It’s reasonable .B、It’s possibl

— Susan ,what do you think of my plan？— _______________A、It’s possible.B、It’s reasonable

He works incredibly hard and yet needs very little sleep—he must have a strong______.A．con

64._________A.impossible B.incident C.incredible

有两个关系R(A B C)和S(B C D) 则R÷S结果的属性个数是__________.