a)cout学号1，输入错!\n;elseif(a=90)cout学号1，等级=A;elseif(a=80)cout学号1，等级=B;elseif(a=60)cout学号1，等级=C;elsecout学号1，不及格\n;if(b0
b)cout学号2，输入错!\n;elseif(a=90)cout学号2，等级=A;elseif(a=80)cout学号2，等级=B;elseif(a=60)cout学号2，等级=C;elsecout学号2，不及格\n;}2.4(改）#includeiostreamusingnamespacestd;intmain(){doublescore;chargrade;inti;for(i=1;i=10;i++){cout请输入分数：;cinscore;if(score0
score)cout输入错误endl;while(score=0score=){if(score=90score=)grade=A;elseif(score=80)grade=B;elseif(score=60)grade=C;elseif(score=0)grade=D;cout学号：iendl;cout等级是：gradeendl;break;}}return0;}2.6#includeiostreamusingnamespacestd;voidmain(){doublea(1),i(2),b(1),c(-1.0),d(-1);for(;i1e-6;){b=c*((-c)*b+2);a=a+1.0/b;i=c/b;c=d*c;}a=4*a;coutaendl;}2.7#includeiostream#includeiomanipusingnamespacestd;voidmain(){inta(0),b(1),i(3),c,count(2);coutab;for(;i=40;i++){c=a+b;a=b;b=c;coutc;count++;if(count==8){coutendl;count=0;}}}2.8#includeiostreamusingnamespacestd;voidmain(){charch;intna,nb,nc,nd,ne,nf,sum;na=nb=nc=nd=ne=0;cout输入一串字符，以#作为结束：\n;do{cinch;switch(ch){casea:na++;break;casee:nb++;break;casei:nc++;break;caseo:nd++;break;caseu:ne++;break;default:nf++;}}while(ch!=#);sum=na+nb+nc+nd+ne;cout元音字母出现的总个数：sumendl;cout元音a出现的总个数：naendl;cout元音e出现的总个数：nbendl;cout元音i出现的总个数：ncendl;cout元音o出现的总个数：ndendl;cout元音u出现的总个数：neendlendl;}2.9#includeiostream#includeiomanipusingnamespacestd;voidmain(){doubleC,F(-30);for(;F=;){C=1.8*(F-32);cout华氏温度：setw(3)F摄氏温度：Cendl;F=F+5;}}2.10#includeiostreamusingnamespacestd;voidmain(){inti;longp,a,b;i=1;p=1;for(;i=5;){p*=i;i++;}a=p*6;b=a*7;cout5!+6!+7!=a+b+pendl;}2.11#includeiostreamusingnamespacestd;voidmain(){intm(2),j(1);for(;j=;m++){for(inti=2;im;i++)if(m%i==0)break;if(i==m){coutm;j=j+1;}}}2.13#includeiostreamusingnamespacestd;voidmain(){inta,b,i(2),n;cout请输入一个整数：;cina;n=a;b=a*(a-1)+1;couta的3次方=b;for(;i=n;i++){b=b+2;cout+b;}}天大机械学生会北京治疗白癜风的需要多少钱北京那家医院治疗白癜风好