【单选题】
It is currently about（）as methanol.
A、twice as expensive as
B、as twice expensive as
C、as expensive twice as
D、expensive as twice as
查看正确答案
A、Current can be determined by measuring the direction and distance between simultaneous EP and DR positions B、The drift of the current should be averaged out on a one hour basis C、After the current is determined，it should not be used for further plotting because it is an unknown variable D、The distance between a simultaneous DR position and fix is equal to the drift of the current
