"Why is it dark now?"
Translation:Pam mae hi'n dywyll nawr?
Pam mae e'n dywyll nawr? wasn't accepted. Should it have been?
Edit to add: Thanks for the quick response, Richard. If that information about the abstract it was in any of the tips & notes, I had forgotten it. (Another edit a couple months later: I see the use of hi rather than e/o/fe/fo mentioned in the tips & notes for the Problems skill a bit further down the tree.)
Pam is followed by mae in the standard language just like other adverbials (sut, ble, pryd, i bwy etc.). However in the colloquial language, it's often followed by bod. There's a Welsh song "Pam fod eira'n wyn?".
Achos and words of similar meaning like gan, am, oherwydd and oblegid are followed by a bod clause. However in the colloquial language you'll hear both achos mae and achos bod.