1. [单选题]位于地理北极的测者，其真北方向为：()
A. 无真北方向
B. 任意方向
C. 向上
D. 向前
2. [单选题]If the bowl of a disk type centrifugal purifier when operated as a separator is not primed, the
A. oil has a tendency to emulsify in the bowl
B. purifier will act as a clarifier at the discharge ring
C. oil will be lost through the water discharge ports
D. oil solids will be deposited only at the intermediate top disk
