Sentence Correction

About twice a month, enough evidence having accumulated, the police would feel obliged to stage a raid.

(A) About twice a month, enough evidence having accumulated,

(B) About twice a month, when enough evidence had been accumulated,

(C) About twice a month, on having accumulated enough evidence,

(D) Twice a month, having accumulated enough evidence,

(E) Having accumulated enough evidence about twice a month,

OA is C I think it should be B. Can someone explain why my choice is bad. OA looks awkward.

check grammar before check meaning logic or die

check grammar

"having done" never follow a noun. A is out

"when ..had been.., would" can not go together. B is out

check meaning logic

"accumulated... twice a month..." is not logic. "twice a month" should refers to "obliged to stage". E is out

C and D are left. I really do not know, "on" is not needed"

IMO D