求指教 - OG2016 SC11

LISAZHANGLUSHA

OG2016 SENTENCE CORRECTING 11:

Coffee prices rose sharply Monday, posting their biggest one-day gain in almost three years, after a weekend cold snap in Brazil raised concern that there could be damage to the world’s largest crop when at a time with supplies already tight.
(A) that there could be damage to the world’s largest crop when at a time with supplies
(B) that the world’s largest crop could be damaged at a time such as when supplies are
(C) that the world’s largest crop could be damaged at a time when supplies are
(D) of the world’s largest crop possibly being damaged at a time with supplies
(E) of possibly damaging the world’s largest crop at a time that supplies were

OG正确答案是c
但是为何 ARE 不改变时态?  前方有 RAISED....

Sisyphus_jwh

因为supplies紧张不是过去发生的事情，而是一个状态，并不是单单指过去紧张，现在应该依旧很紧张