You can use it! But because you can say nosotros and nosotras, they want you to say both answers!
You don't have to worry because "nadamos" alone will already be understood as "we swim"
You can. You have to select all the correct answers. There are two. Nosotros is we masculine plural or we all of us, plural (males & females) & nosotras is we feminine plural (just a group of girls).
I'm so confused with the word for swim. In previous question it used nada and nadan for the same questions, but when I use it it's apparently ALWAYS wrong! :'(