Because the management of the large corporation will often refer to macroeconomic forecasts when it plans for the future, it is probable that its belief in their soundness is significant
A) it is probable that its belief in their soundness is significant
B) it is probable that the soundness of their belief would be significant
C) believing their soundness is probably not significant
D) the significance of their belief on its soundness is probable
E) its belief in their soundness is probably significant
we can eliminate A?B because "it is", "there is/are", "here is/are" are normally incorrect and wordy.
C is awakward. D has wrong pronoun referent. "their" does not agree with mgmt.
E is correct, concise and short.