不一定,有可能用whether,具體看語句的意思,同位語從句常放在fact,news,idea,truth,hope,problem,information等名詞后面,說明該名詞的具體內(nèi)容,給你幾個(gè)具體的用that或者whether的例子,自己體會(huì)下吧.你也可以去找些語法書來更系統(tǒng)的研究下.
　　1.如同位語從句意義完整,應(yīng)用that引導(dǎo)同位語從句.
　　例：The general gave the order that the soldiers should cross the river at once.將軍下達(dá)了戰(zhàn)士們立即過河的命令.
　　2.如同位語從句意義不完整,需增加"是否"的含義,應(yīng)用whether引導(dǎo)同位語從句.
　　例：We'll discuss the problem whether the sports meeting will be held on time.我們將討論運(yùn)動(dòng)會(huì)是否會(huì)如期舉行的問題.
　　3.如同位語從句意義不完整,需增加"什么時(shí)候"、"什么地點(diǎn)"、"什么方式"等含義,應(yīng)用when,where,how等詞引導(dǎo)同位語從句.
　　例1：I have no idea when he will be back.
　　例2：I have no impression how he went home,perhaps by bike.