求助英語問題

___is often the case with a new idea, much preliminary activity and optimistic discussion produced no concrete proposals. Km=dId7]  
A that, B it, C this, D as GW[g!66^  
pm.Zc'23  
which one is the answer? thanks!

D吧

D，應該是

應該是as

是 D

應該是D

選D

我也覺得是D

應該是D

用排除法，應該是d