证券经纪业务是指证券公司通过开立证券营业部接受客户的委托，帮助客户进行风险管理和投资咨询，并根据市场风险控制代理客户做出交易委托。 ( )

Sydney promised her that he would always do anything he could for her to ____of her happiness.

[      ]

A. making sure

B. be sure

C. being sure

D. make sure