If r and s are integers and rs+r is odd, which of the following must be even ？（）
A: r
B: s
C: r+s
D: rs-r
E: r2+s
A: r
B: s
C: r+s
D: rs-r
E: r2+s
举一反三
- If r and s are integers and rs+r is odd, which of the following must be even A: r B: s C: r+s D: rs-r E: (E) r2+s
- 对于可控RS触发器，当RS触发器状态不确定时 ________。 A: S=0;R=0 B: S=0;R=1 C: S=1;R=0 D: S=1;R=1
- 两个与非门构成的基本RS触发器的约束条件为（） A: R+S=1 B: R+S=0 C: R·S=1 D: R·S=0
- 两个与非门构成的基本RS触发器的约束条件为（ ）。 A: R+S=1 B: R+S=0 C: R·S=1 D: R·S=0
- 设有关系R、S和T如下。关系T是由关系R和S经过______操作得到的。RTABCR.AR.BR.CS.AS.BS.Ca1b1c1a1b1c1a1b2c2a1b2c2a1b1e1a1b3c2a2b2c1a1b1c1a2b2c1Sa1b2c2a1b2c2ABGa1b2c2a1b3c2a1b2c2a1b2c2a2b2c1a1b3c2a2b2c1a1b2c2a2b2c1a2b2e1alb3c2a2b2c1a2b2c1 A: R∪S B: RS C: R×S D: R∩S