Tom was about to close the window______________ his attention was caught by a  bird.   [ ]

A. when    

B. if    

C. and    

D. till

私人银行客户信用贷是依据私人银行客户金融资产给予的无担保信用贷款，应与客户签署《客户承诺书》。当客户AUM资产发生变动且低于贷款余额2倍的预警线时，私人银行客户经理应自知晓AUM变动时点起第一时间向个贷中心作出风险提示。