"Do not tell your mother!"
Translation:Peidiwch â dweud wrth eich mam!
Verbs/verb-nouns are used with particular prepositions to create particular meanings. Here, dweud wrth means 'telling/saying (to)'. With am it means 'saying/telling about'.
- Dw i'n dweud wrth Siân am y ddrama - I am telling Siân about the play
Another example is siarad â ... am... (speaking to ... about...) (not siarad wrth)
- Dw i'n siarad â hi am y ddrama - I am speaking to her about the play
This is a command. It simply means 'don't tell' (don't say to) 'your mother'
This is something a parent might say to a child for example. eg
'Don't tell your mother about the party'
why is the "chi" form given as the ideal answer?
Surely the "ti" form would be used if talking to a child, and if somebody's talking to an adult in this manner, I would expect that they know the person well enough to call them "ti" . . .
Remember that chi would be used if you were talking to two or more children or adults, too, even if they were familiar.