4.给定A={1,2,3,4},A上的关系R={(1,3),(1,4),(2,3),(2,4),(3,4)}满足的性质是（）

下面代码的输出结果是()s=["seashell","gold","pink","brown","purple","tomato"]print(s[1:4:2])

地下水按埋藏条件分类，包括（）。

以下哪些属于工程地质条件范畴？（）

水泥的体积安定性，即指水泥浆在硬化时（）的性质。

类Test1定义如下：1.publicclassTest1{2．publicfloataMethod(floata,floatb){}3．4．}将以下哪种方法插入行3是不合法的。（）

1.TheworldisquicklyrealizinghowmuchitdependsonChina.2.Appleisreroutingsupplychains.Ikeaisclosingitsstoresandpayingstaffmemberstostayhome.Starbucksiswarningofafinancialblow.FordandToyotawillidlesomeoftheirvastChineseassemblyplantsforanextraweek.3.Themysteriouscoronavirushasvirtuallyshutdownoneoftheworld’smostimportantgrowthengines.Desperatetoslowthefast-movingvirus,theChineseauthoritieshaveextendedthecountry’snationalholiday,andcrippledland,railandairtransport.Entirecitieshaveshutdown.4.Thefullextentofthehittothebroaderbusinessworldisnotyetclear.“Ourmembersaredealingwithvaryingdegreesofdisruptionintheirbusinesses,”saidJakeParker,theseniorvicepresidentoftheUS-ChinaBusinessCouncil.5.Iftravelrestrictionsandquarantinesareexpandedortheholidayextendedfurther,hesaid,“thatwillamplifytheseproblems.”Question:Whichofthefollowingcanbestreplace"virtually"in"Themysteriouscoronavirushasvirtuallyshutdownoneoftheworld’smostimportantgrowthengines"?

1.TheworldisquicklyrealizinghowmuchitdependsonChina.2.Appleisreroutingsupplychains.Ikeaisclosingitsstoresandpayingstaffmemberstostayhome.Starbucksiswarningofafinancialblow.FordandToyotawillidlesomeoftheirvastChineseassemblyplantsforanextraweek.3.Themysteriouscoronavirushasvirtuallyshutdownoneoftheworld’smostimportantgrowthengines.Desperatetoslowthefast-movingvirus,theChineseauthoritieshaveextendedthecountry’snationalholiday,andcrippledland,railandairtransport.Entirecitieshaveshutdown.4.Thefullextentofthehittothebroaderbusinessworldisnotyetclear.“Ourmembersaredealingwithvaryingdegreesofdisruptionintheirbusinesses,”saidJakeParker,theseniorvicepresidentoftheUS-ChinaBusinessCouncil.5.Iftravelrestrictionsandquarantinesareexpandedortheholidayextendedfurther,hesaid,“thatwillamplifytheseproblems.”Question:whichofthefollowingsentenceshastheword"idle"withthesamemeaningandusageasthatin"FordandToyotawillidlesomeoftheirvastChineseassemblyplants?"

python3解释器对列表[1,2,[3,4],5,6]使用reverse方法执行的结果为()。A[6,5,[3,4],2,1]B[6,5,[4,3],2,1]C[6,5,2,1,[3,4]]D报错

现有代码t=(1,2)，在python3解释器中执行t*3得到的结果为():A语法错误B(1,2,1,2,1,2)C(2,4,2,4)D以上说法都不对

表达“从一个关系的所有行中提取出满足某些条件的行”，“从一个关系的所有列中提取出某些列”“提取出属于一个关系但不属于另一关系的所有元组”“将两个关系必须按照某种条件串接成一个较大的关系”的操作依次是（）。1、并2、交3、积4、选择5、投影6、差7、连接

执行下列语句后a的值为（）inta＝5,b＝6,w＝1,x＝2,y＝3,z＝4;(a＝w>x)&&(b＝y>z);

类Test1定义如下：1.publicclassTest1{2．publicfloataMethod(floata,floatb){}3．4．}将以下哪种方法插入行3是不合法的。（）

给出下面代码：　　1:classParent{　　2:privateStringname;　　3:publicParent(){}　　4:}　　5:publicclassChildextendsParent{　　6:privateStringdepartment;　　7:publicChild(){}　　8:publicStringgetValue(){returnname;}　　9:publicstaticvoidmain(Stringarg[]){　　10:Parentp=newParent();　　11:}　　12:}　　那些行将引起错误？()

以下程序的输出结果是（）main(){intx＝2,y＝－1,z＝2;if(x<y)if(y<0)z＝0;elsez+＝1;printf(“%d\n”,z)}