"Fyddi di yn ffonio Ceri Lingo?"
Translation:Will you phone Ceri Lingo?
Yes. An interrogative verb undergoes soft mutation.
( This is due to the 'ghost' of the interrogative particle a (not a = and) which is still used in the literary and formal spoken language. Even though it is not used in colloquial speech and writing, the soft mutation which it causes remains:
- A oes heddwch? (Is there peace?)
A drefnodd ysgrifennydd y cwmni'r cyfarfod? (Did the company secretary arrange the meeting?
(A) Dacslusaist ti'r teganau?
- (A) Fyddi di'n ffonio Ceri?
- (A) Wnaeth Ceri brynu ffôn newydd? (Did Ceri buy a new phone?)