應(yīng)填B：isn't it.
原因：
含有think,believe,suppose,imagine,expect等動詞后接賓語從句構(gòu)成的主從復(fù)合句在構(gòu)成反意疑問句時(shí),視情況不同有兩種不同的構(gòu)成方式.
(1.)當(dāng)主句的主語為第一人稱時(shí),其后的簡短問句應(yīng)與從句相一致.例如：
I expect our English teacher will be back this weekend,won't she/he?
We suppose you have finished the project,haven't you?
值得注意的是,當(dāng)這些動詞后接的賓語從句的否定轉(zhuǎn)移到主句時(shí),其仍屬否定句,故其后的簡短問句應(yīng)用肯定式,而非否定式.例如：
I don't believe that he can translate this book,can he?
Wedon't imagine the twins have arrived,have they?
此類句子的回答同"前否后肯"型反意疑問句一樣,如上述后一個(gè)句子,若雙胞胎已經(jīng)到了,則回答為"Yes,they have."；若尚未到達(dá),使用"No,they haven't.".
(2).當(dāng)主句的主語為第二、三人稱時(shí),其后的簡短問句則應(yīng)與主句相一致（此時(shí),否定只看主句,與從句無關(guān)...）.例如：
Your sister supposes she needs no help,doesn't she?
You thought they could have completed the project,didn't you?
They don't believe she's an engineer,do they?
She doesn't expect that we are coming so soon,does she?
而本題屬于第二種情況,故答案為B.