從句如果是陳述句，一般選擇連詞that，這里that 沒有實際的意義，只是連接兩個句子。所以，也可以把它省略掉。比如We all expect that they will win.

如果要表示是否的疑問語氣的賓語從句，就要選擇if或者whether.比如Nobody knew whether he could pass the exzam.

如果從句本身缺少主語，或者賓語，或者定語，或者表語等，就要選擇疑問代詞如who whom whose what whoever whomever whosever whatever 等。比如I don't know whom you should depend on.

根據(jù)意思和疑問語氣，還可以選擇疑問副詞when where how why whenver.wherever however.比如He didn't tell me when we should meet again.

值得注意的是，what whatever 一般是指疑問，但也可以指陳述。比如The book will show yon what the best CEOs know.