有以下程序，若想通过键盘输入，使得a1的值为12，a2的值为34，c1的值为字符a，c2的值为字符b，程序输出结果是：12，a，34，b。则正确的输入格式是(选项中的代表空格，＜CR＞代表回车)

#include＜stdio.h＞

main（）

{ int a1, a2; char c1, c2;

  scanf("%d %c%d%c", &a1, &c1, &a2, &c2);

  printf("%d, %c, %d, %c’, a1, c1, a2, c2);

}

A.

B.

C.

D.

Originally, the World-Wide Web was designed as information medium for (71) research teams. A deliberately simple implementation model was chosen to make it as simple as possible for authors to (72) documents to the web, and to (73) these in the sense of updating content. This implementation model is centered around the notion of resources, usually file-base D. For the (74) intended use of the web, resources presented a useful abstraction, as they related to relatively self-contained chunks of information such as research publications and (75) pages. Such chunks of information typically could be set up and maintained independently of other resources, so that resources were the appropriate abstraction for composition and modification.

（72）（）

A.contribute

B.write

C.hand

D.make