请教GWD上的一道语法题

请教大家，此题答案为什么是C啊，不是说宾语从句必须有that 的么？

（GWD 17的23题）

Trans World Entertainment Corporation, which owns
        the Record
                Town and Saturday Matinee retail chains,
        announced that since sales of up to one-fourth of its stores are poor, they will be closed.

A.    that since sales of up to one-fourth of its stores
        are poor, they will be closed.

B.    it is closing up to one-fourth of its stores, which
        accounted for its poor sales

C.    it was closing up to one fourth of its stores
        because of poor sales.

D.    to be closing, on account of poor sales, up to one-fourth of its stores.

E.     having poor sales, such that up to one-fourth of its stores will be closed.

请哪位帮忙解答下：）

为什么没人理啊

是问得太低级么

非常感谢~~

我之前也看了不少讨论，但是没有发现这题，能告诉我位置么：）