"My sister is a secretary."
Translation:Моя сестра - секретар.
If you read tips and notes, you would knew :) We can use masculine versions of professions to refer to women. When you use masculine noun you're just talking about one's profession. If you choose to use feminine version it's like you're accentuating the gender of a person.
I think we need to be careful here not to let Russian norms slip into Ukrainian. It is completely normal to speak with feminitives and Ukrainians do it automatically. That being said, it's not a wholly balanced practice, as professions generally associated with women more likely to be "feminized," but nearly all names of professions lend themselves to this.
But many Ukrainian feminists argue that we SHOULD use words like секретарка to emphasize the presence of women in the professional world. Perhaps secretarial positions don't serve well here, but лікарка, for example, shows us that there are women in the medical field, and not just as медсестри.
I think the first choice using секрктарка would be wrong because the beginning of the sentence "Мий сестра" uses case wrong. I think "Моя сестра - секрктарка " would have been correct.