对一个句子的结构不理解,

题目

对一个句子的结构不理解,
The account holder must start withdrawals by age seventy and one-half or there also are fines.请问withdrawals,经查字典是名词,但奇怪为什么start动词后面可以加名词呀,通常是start+to do sth,

答案

户主必须到71.5岁后才能开始提款否则依然会有罚金.
这里是活用了start doing sth.,withdrawal是withdraw这个动词的名词形式.