Wouldn't it be this bush has A good smell? In the word selection exercise it was just this bush has good smell...that doesn't sound right in English.
Yes, that is bad English. The noun needs an indefinite article (a). The funny thing is, my English mind simply inserted the 'a' in the sentence, so I didn't notice until you pointed it out.
Yay! The word "scent" is also accepted! (The bush could have flowers on it that give it a scent...they grow in my part of Yerushalayim, near the forest.)
Thank you, Duolingo!