為你解答.
1.Do you know . Does Tom live in this city?
Do you know（if） Tom （lives） in this city?

2.Could you tell me ... Is it polite to eat noisily in Japan?
Could you tell me （whether ）（it's）（ polite）to eat noisily in Japan ?

3.I don’t know ... Did they have a good time at the party yesterday?
I don’t know （if） they （had）a good time at the party yesterday.

4.I want to know ... Will they come back from Beijing tomorrow?
I want to know （whether） they（will）come back from Beijing tomorrow.

5.I can’t remember ... Was he late for work yesterday or not?
I can’t remember（whether） he（was）late for work yesterday or not.
第五題因為有or not,只能用whether作為引導(dǎo)詞.
前四句的if\whether可以換用.