"Co wolisz"? In another exercise, "prefer" was accepted as a translation of "bardziej lubić".
Hmmm... okay, added.
Is lub not correct in place of czy?
In questions, where you have to choose one option, czy is always used.
So these always end in anie or enie?
Gerunds? Yes, either always or almost.
"wiecej" should be acceptable --to me, it means MORE!
The English word "more" expresses two concepts: quality and quantity. Bardziej is just for quality, whereas więcej is just for quantity.
If you read carefully, you will see that this question has already been answered in the comment section.
why not co podoba ci się bardziej - czytanie czy pisanie?
It kinda sounds to me like you were talking to a primary school pupil who is learning both and they're new abilities to them... but it's a valid interpretation, I guess. Added.
Thanks. It's hard to think of a different interpretation? I cannot see myself ever asking an adult that question.
why "co" rather than "ktory"
"który" means "which", not "what". Maaaaaaaaybe we could justify using it here, but it should at least be "Które" to match how those verbal nouns are neuter. But still it doesn't sound like a good idea to me, it would still sound strange.
I tried "Które" instead of "Co", We frequently are told in this course that które is for a closed set of options. But it doesn't work here?
Well, I think this is one of the reasons why we're so strict about keeping forms of "który" to "which". Maybe it wouldn't be wrong to use "Które" here, but it sounds rather strange to my ear.