"Does your dog fall often?"
Translation:An dtiteann do mhadra go minic?
Odd how many of the alternatives in the Irish version of Duolingo are nonsense sentences - in the French version they're good sentences, and often there are two correct choices, eg between singular and plural person
If your sole objective is to learn a list of pre-formed sentences off by heart that you can trot out when needed, then, of course, these so-called "nonsense sentences" are a waste of your time. If your objective is to learn a language, and get a feel for how it's structure works, and differs from your primary language, then the occasional "nonsense sentence" can be advantageous - it can help you focus on how something is said, rather than what is being said. It also makes it easier to remember that particular structure.
I'm not entirely sure what your second point is about, but lots of the "Mark All Correct" exercises have 2 correct answers, some because of tú and sibh forms, and some because of dialect variations.
Sneaky throwing gadhar (hound) in there! I almost missed the grammatical mistake in that sentence, I was so focused on the unusual alternative for madra.
(I was offered An dtiteann do ghadhar raibh minic? in a "Mark All Correct Translations" exercise)