At the railway station，the mother waved goodbye to her daughter until the train was________.

A．out of sight

B．out of reach

C．out of order　　

D．out of place

吐温类表面活性剂的化学名称是

A．三油酸甘油酯类
B．山梨醇脂肪酸酯类
C．聚乙烯脂肪酸酯类
D．失水山梨醇脂肪酸酯类
E．聚氧乙烯失水山梨醇脂肪酸酯类