"Who is going to the afternoon meeting?"
Translation:Pwy sy'n mynd i'r cyfarfod prynhawn?
Wedi awgrymu Pwy sy'n mynd i gyfarfod y prynhawn? fel ateb cywir arall.
The English is grammatically ambiguous - "afternoon" can be an adjective or a genitive possessor - not that it's likely to matter, or even occur to most speakers. It's only an issue when you translate it into Cymraeg and pick the wrong position for the definite article, like I just did.