单项选择题
A.in which
B.on which
C.to which
D.by which
单项选择题 The fire drill must, as far as practicable, be conducted if （）.
单项选择题 （）, the second one will start automatically.
单项选择题 Changes in direction or speed of the main propulsion units shall be recorded, （）an Administration has determined that the size or characteristics of a particular ship make such recording impracticable.