Cash flows to stock and bond mutual funds have gained strength in the last two months, but fund managers have not been eager to invest the new money, instead of preferring to raise the cash levels in their portfolios at the highest level in six months.
A.have not been eager to invest the new money, instead of preferring to raise the cash levels in their portfolios at
B.have not been eager to invest the new money, instead preferring to raise the cash levels in their portfolios to
C.have not been eager at investing the new money, instead of preferring to raise the cash levels in thief portfolios to
D.were not eager to invest the new money, instead of preferring to raise the cash levels the cash levels in their portfolios at
E.were not eager at investing the new money, instead preferring to raise the cash levels in their portfolios to
答案是B，我的问题是preferring在句子里做伴随状语吗？我记得prep中说伴随状语不跟完成时态的啊，那如果不是伴随状语，在这里做什么成分呢？求nn们指教！ | 
