_____are not leached out of soil,reclamation procedures are needed to restore the land'sproductivity.
A)For concentrations of salt
B)Salt concentrations that
C)If salt concentrations
D)With concentrations of salt
答案是C,为什么不选A,我觉得因果和条件关系都说得通,难道只能用salt concentrations而不能用concentrations of salt?请高手指点.