{a, b, c, d, e}, A= {a, b, c, d}, R=
{(a, a), (b, b), (c, c), (d, d), (e, e), (a, b), (d, c), (b, c ), (a,
c), (e, b), (a, d), (e, d), (e, a), (e, c)}, 求(X,R)的cover
A. Cover={ ( a, b), (b, c), ( a, d), ( e, a ), ( e, b ) } B. Cover={ ( a, b), (d, c), (b, c), ( a, d), ( e, a )} C. Cover={ ( a, c), (d, c), (b, c), ( a, d), ( e, a )} D. Cover={ ( a, b), (d, c), (b, c ),( a, c), (e, b), ( a, d), (e, d), (e, a), (e, c )}
举一反三
- SPEAK : DRAWL:: A: (A) eat : sip B: (B) run : canter C: (C) lament : sigh D: (D) gain : cover E: (E) look: glance
- is the last part of a paper to write. A: Abstract B: Keywords C: Reference D: Acknowledgement E: Cover letter
- 设集合X={a,b,c,d,e}，集合X上的二元关系R={(a,b),(b,c),(c,d),(d,e)}，则R的传递闭包为[img=44x21]180380e93cb7cf8.png[/img]{(a,b),(a,c),(a,d),(a,e),(b,c),(b,d),(b,e),(c,d),(c,e),(d,e)}。
- Journal is to article as () A: dance is to ballet B: magazine is to cover C: set is to scenery D: anthology is to poem E: concert is to orchestra
- SPEAK: DRAWL :: A: eat: sip B: run: canter C: lament: sigh D: gain: cover E: look: glance
内容
- 0
有两个在关系模式R(A,B,C,D)和S(A,C,E,G),则X=R×S的关系模式是()。 A: X(A,B,C,D,E,G) B: X(A,B,C,D) C: X(R.A,B,R.C,D,S.A,S.C,E,G) D: X(B,D, E: ,G)
- 1
设A={a,b,c,d,e}，有一个划分S={{a,b},{c},{d,e}}，由划分S确定A上的一个等价关系R为（ ） A: {〈a,a〉,〈b,b〉,〈c,c〉,〈d,d〉,〈e,e〉,〈a,b〉,〈b,a〉} B: {〈a,a〉,〈b,b〉,〈c,c〉,〈d,d〉,〈e,e〉,〈a,b〉,〈b,a〉,〈d,e〉,〈e,d〉} C: {〈a,a〉,〈b,b〉,〈c,c〉,〈d,d〉,〈e,e〉,〈a,b〉,〈d,e〉,〈e,d〉} D: {〈a,a〉,〈b,b〉,〈c,c〉,〈d,d〉,〈e,e〉, 〈b,a〉,〈d,e〉,〈e,d〉}
- 2
设有关系模式R（A，B，C，D，E），F={A→B,E→A,CE→D},则R的候选键为（） A: {A,E} B: {A,C,E} C: {C,E} D: {A,B} ,{C,E}
- 3
已知集合A={a,b,c,d,e}，A上的一个划分是：{{a},{b,c},{d,e}}，请写出该划分对应的等价关系R： A: {(a,a),(b,b),(c,c),(d,d),(e,e),(b,c)(c,b),(d,e),(e,d)} B: {(a,a),(b,b),(c,c),(d,d),(e,e),(a,b),(a,c),(b,a),(b,c),(c,a),(c,b),(d,e),(e,d)} C: {(a,a),(b,b),(c,c),(d,d),(e,e),(a,b),(b,a),(d,e),(e,d)} D: {(a,a),(b,b),(c,c),(d,d),(e,e),(b,c),(c,b)}
- 4
a.股骨b.耻骨c.坐骨d.髂骨e.距骨 A: a，b，c B: a，b，e C: a，d，e D: b，c，d E: c，d，e