You have to take some necessities such as ropes, a flash, boots, ______ you may get lost in the mountain if going hiking.

A．so that

B．in order that

C．now that

D．in case

甲、乙、丙、丁是四个体积、形状相同而材料不同的球，把它们投入水中静止后情况如图所示，它们中受到浮力最小的是

A. 甲　　

B. 乙　　

C. 丙　　

D. 丁