Is "os mae gen ti amser" not possible, does it have to be bydd?
Os mae gen ti amser is fine here
Previous sentences had fydd... after os; this one has bydd. what's the rule?
There is no mutation after 'Os' so "os bydd" is the only correct version, if you see a different one please report it and we'll edit the sentence. Thanks for bringing this up.
Just to clarify - if the sentence is negative, mutation would be appropriate, right?
Os fydd gen ti ddim amser, for example, for "if you will not have time"?
Yes, that's correct
I wish the corrections were a bit smarter!
I typed Gobeithio, os fydd gynnoch chi amser and was corrected to os MAE gynnoch chi amser, rather than os BYDD.
I realise there's likely nothing the course maintainers can do about this though.
We have 22 alternative answers to this sentence and using 'mae' is a valid alternative. Our fault really for not putting more context in this sentence, ie yfory, heddiw.