问题
单项选择题
You have berthed in a area with other tank vessels. What signal is displayed by a vessel to indicate it is transferring flammable or combustible liquid cargo?（）.
A.A flashing yellow light
B.A red light visible all around the horizon
C.A green light visible all around the horizon
D.An illuminated red and yellow caution flag
答案
参考答案：B
糙的水平地面上，在斜劈上放一重为G的物块，物块静
止在斜劈上，今用一竖直向下的力F作用于物块上，下列说法正确的是 （ ）