一道英语题Help!!!!Help!!!!在线等！！！！！

____for computers is called computer programming.
A Write instructions B To write instructions
C The writing of instructions D Having written instructions

为什么是B
pbty00: 为什么C答案writing前不加定冠词？？？？

A是动词做谓语芹源镇
B是动词不定式可以做主语
C应是 writing instructions
D语法上没错不裂衡符合逻嫌粗辑

writing of 这个有问题
主语变成writing了模吵
但是雀乎B是个动作
如果C是旦岁侍writing instructions就更加好，不过…………现在这样只有B了