"Run" should be acceptable here as well, shouldn't it?
It really should be, but Duolingo makes you match punctuation, so with a period this can only be a sentence.
Ah. That was sneaky. ;)
Ahhh thank you, I'll have to keep my eye on the punctuation!
Ah that caught me off guard too
Introducing the past tense right off the bat? That's different.
Since there is no tense, all sentences are potentially in the past tense, so it's impossible not to introduce past tense right from the start.