"I have never done that."
Translation:Nunca he hecho eso.
Alexandra - Because you do not know the gender of THAT. The default (neuter) form of THAT is ESO. Yeah, it's confusing. :P You would only use ESA if you clearly knew from context that THAT is referring to something feminine.
ESE - masculine ESA - feminine ESO - neuter
Hope that helps. :-)
I thought it possible as well, since it isn't a standalone sentence, that is, I inferred that two or more people were talking and they knew what "that" refers to, very possibly something with feminine gender. Example: I have never made that (cake)/nunca he hecho esa (torta).
LizGish: "he" (I have) is the first person singular conjugation of "haber" (to have). "Hecho" is the past participle of "hacer" (to make, to do...). As rogercchristie explained, "(yo) he hecho" translates as "I have done" or "I have made."
Our friends at duolingo should have included a short explanation of the rules on the Present Perfect lessons page as they did for the Phrasal Future Tense lessons page.