签订保证贷款合同的主要风险点是主从合同签订。（）
参考答案：对
The nurse whose name is Mary assisted me ______ the operation they day before yesterday.
A．perform
B．to performing
C．on performing
D．in performing
长期使用会造成牙色素沉积的药物牙膏是
A．“全效”牙膏B．氯己定牙膏C．脱敏牙膏D．氟化亚锡牙膏E．增白牙膏
