"Give me two eggs."
Agreed, and chicken is the default. In Taiwan, I almost never hear someone call regular eggs "ji dan". I'm certain duolingo will update this... just wish progress could move a little faster. 16 nov 2018.
And I'm the moron for having missed that the "ji dan" characters were also presented as an option beside the lone "dan".
There is a discrepancy with another excersize that offers the chinese "这些鸡蛋不新鲜。" and accepts "These eggs are not fresh" as correct.
Brings up an interesting learning note for @duo @duolingo: there must be allowed a range of answers, but there is a specific answer that is the literal "best translation" which ought to be always taught for the lesson (and usually is, excepting blups and brain farts like "我们想买东西" to inaccurately include the words "go shopping" in that particula lesson--it's entirely possible to be referring to an unactioned desire or online buying from home in the Chinese statement which gets excluded from the current Duolingo norm).
The Edu note is to allow mind the ability to drop unnecessary words as is taught in later lessons when more information is added to sentences and context itself is used for reference in place of superfluous characters.
Is the 鸡 always needed? It can't be just 蛋? I suppose "egg" usually refers to chicken eggs, but it could be any type of egg?
粒 is used as a measure word for large round objects in some dialects like Min, but not in Mandarin.
No. In Mandarin "li" refers to much smaller objects, such as rice. You can say 两粒米. In case of eggs, you can use “颗”, the measure word for medium to big size ball shape objects, or the very generic measure word "个”.