集中作业平台系统支持（）天内的业务受理凭证补打。

A、30

B、31

C、60

D、90

Mary A Contrary has a SHORT position in 15 November heating oil contracts. She buys 15 December heating oil contracts. Ms. Contrary has:()

A. closed her futures position by offset. 

B. initiated a new LONG futures position in addition to her existing SHORT position. 

C. initiated an exchange-for-physicals (EFP).