在图中，画出静止在水面上小球的受力示意图。
Let's ______ a sandwich together. [ ]
A. to do
B. do
C. to make
D. make
A．既小于R1又小于R2
B．既大于R1又大于R2
C．小于R2而大于R1
D．等于R1与R2之和
