It is how conocer is conjugated. You have to be prepared to look up conjugations of verbs or just note them as Duo introduces a new one.
conocer is an irregular verb and the irregular verbs must be memorized http://www.spanishdict.com/conjugate/conocer although there is also a rule about c's and vowels. As far as the 'a afterwards' it is really an a - the personal a - used before people references. see here: http://www.bowdoin.edu/hispanic-studies/tools/newgr/ats/21.htm
Maybe because although similar in meaning they are actually not the same are they? There is a Slanish word - in fact there are two - for "never" so as this is a Spanish course the absence of either of those words suggests you don't put "never" in the English translation.
Because it is present time.
And the second point is, that "conocer" in a sentence with a negated meaning like this I am pretty sure that it is translated by "to know". Concerning this second point it would be fine to have a spanish native (I'm not) opinion or a DL one ...
'I haven't met your girlfriend" would make it Present Perfect , which would then be "No he conocido a tu novia".
From Spanishdict.com (great reference website):
The Spanish present perfect (el pretérito perfecto compuesto) is used to talk about things that started in the past and which continue or repeat in the present.
"Yo no conozco a tu novia" is Simple Present so simply means "I do not know your girlfriend."
I am not familiar with your girlfriend was marked wrong! When that phrase was used in a preceding question!
“i didn’t meet your girlfriend” - marked wrong.
in an earlier exercise duo marked me wrong for using “know” instead of “meet” for conozco. weird.
First of all, meet vs know is dependent on context. Second, "I didn't meet your girlfriend" is technically past tense, and the current exersize is present tense. Your entry would translate to something closer to "Yo no conocí a tu novia."
Estelle0 I wrote "No conozco a tu novia." Cannot believe this is marked incorrect. The Duolingo person who marked this wrote as follows: "You missed a word"--followed by the sentence as above with the word 'no" underlined--if I missed it why is it underlined????? PLEASE let me know how to report this!!
No, it is your....no accent....and it is a good question....why not "no conozco a tu novia"
"Tú" is a personal pronoun. It is the personal pronoun for you (informal): "Tú estas aquí" = "You are here"
"Tu" (no accent) is an informal possessive adjective. "Tu casa" - your house.
Mi casa; mis casas
Tu casa; tus casas
Su casa; sus casas
Nuestra casa; nuestras casas
Su casa; sus casas (su is used for he, she, you formal and their)