We can ask a rhetorical question using the structure 难道…吗 .
We should state 难道 at the beginning of a sentence or a phrase and use the question particle 吗 at the end.
We should use the predicate in the negative form.
Rhetorical questions are questions where an answer is not really expected. It is often used to express indignation or astonishment.
Don't you believe we will win?
nándào nǐ bù xiāngxìn wǒmen huì yíng ma
He's lying to you, can't you see that?
tā zài piàn nǐ, nándào nǐ kàn bu chūlai ma
The adverb 莫非
We also can use the adverb 莫非 to ask a rhetorical question that expresses surprise. It is used less frequently than 难道.
We should state 莫非 at the beginning of a phrase or sentence.
In sentences with 莫非, we should not use the question particle 吗.
Could it be that I’m wrong?
mòfēi wǒ cuò le
Do you think I'm a liar?
mòfēi nǐmen juéde wǒ shì ge piànzi
He has not been feeling well lately. Could it be that he is really getting old?
tā zuìjìn shēntǐ bù hǎo, mòfēi zhēn de shì lǎo le
The modal particle 不成
To form a rhetorical question, we can also state 不成 at the end of a sentence.
We usually use it with the following constructions:
Are we not allowed to speak?
nándào bùxǔ wǒmen shuōhuà bùchéng
She didn't come today, is she sick again?
jīntiān tā méi lái, mòfēi yòu shēng le bìng bùchéng