答案：CABCB

词汇讲解

1.  initially 最初,开头

She came initially to spend a few days, but in the end she stayed for a whole month. 
起先她只打算来待几天，但後来却住了整整一个月。

Initially, I disagree with his proposal, but later I changed my mind. 
起初我不同意他的提议，不过后来我改了主意。

2.  optimism  乐观,乐观主义

Her mood varied from optimism to extreme depression. 
她的情绪由乐观一变而为极度消沉.

They professed optimism about the outcome. 
他们对结果表示乐观.