
Anuj B. answered 12/23/19
"Best German Student" at UT Austin + 5 months studying in Germany!
Hi Mark - the distinction here is whether or not the party being spoken to is "du" or "ihr". If the party being addressed were "du" then "tue" would be the correct form of the imperative (not "tu"). It seems like this website you are studying with may have intended for the addressee to be identified as "ihr", in which case the correct form of the imperative would indeed be "tut".
I'm not familiar with the website you mentioned, but a good way to weed out websites that may not be helping you learn German as much as you think they are is to evaluate whether they are sufficiently distinguishing between the different modes of address in German (du, ihr, Sie, etc.). Hope this helps!