下列不构成无限循环的语句或语句组是( )。

A．n=0;do {++n;} while (n＜=0);

B．n=0; while (1) {n++;}

C．n=10;While (n); {n--;}

D．for(n=0, i=1; ;i++)n+=i

Dear Prof. King,

Allow me to introduce to you Mr. Liu, the bearer of this letter. He is one of my former students and is going to enter your institute after graduation here. Will you please give him some necessary guidance about the entrance examination I shall be much obliged if you will show him any favor.

Yours

Alice

What does "obliged" mean（）