The correct answer given when I was marked incorrect used "we've to" which I assume is a contraction of "we have to". I don't think I've ever seen it used in English, and if it has been it is definitely archaic.
Please add all missing correct answers as soon as possible. It is frustrating for the learner, if correct answers are marked as wrong! F.e.: "We will have a match next month, now we have to practice every day."
It's "correct" but it's very old fashioned formal English. No one would say that today. Sounds like some of these translations are being written by non-native speakers using a 100 year old grammar book.
British and Aus English spells the verb 'Practise' with an 's', and the noun Practice with a 'c'. American English avoids the 's' usage. As an Aussie, I'm being forced to use American spelling to get this one correct.