莫非 (could it be that …?)

Don't tell me you forgot…

• can it be possible that莫非mò fēi + (clause)? = "could it be that …? / don't tell me …".
• can it be possible that莫非mò fēiyou你nǐto forget忘wàng(completed / change)了le？ = "could it be that you forgot?"
• can it be possible that莫非mò fēi floats a surprised guess, half-expecting it's true.

Subj + can it be possible that莫非mò fēi + rhetorical question

• can it be possible that莫非mò fēi voices a sudden, uneasy suspicion.

could it be莫非mò fēiyou你nǐforget忘wàng了le？

• can it be possible that莫非mò fēiyou你nǐto forget忘wàng(completed / change)了le？ = "could it be that you forgot?"

Recap

Read the full reference: HSK 6 grammar — Sentence patterns.