It says kau... shouldn't it be kamu?
You singular: kamu, kau
You plural: kalian
"Kamu" is generally more common and more polite than "kau". It's better to use "kamu"
Kau is only found in textbook or in movies subtitles, people dont usually speak "kau" in daily
In my version it says kalian .. but kau is also another (informal) way to say "you"
all my friends fell.
Why does it say kalian for the word "you"?
Kalian means you (plural). As in y'all or youse
Given the lack of context, I argue that all forms of "you" should be accepted considering that a 2-term sentence lacks much information. On the other hand, there might be further background information I lack in putting forward such an argument.
You is kamu[indonesian]
"You" can also be "kalian" if "you" refers to more than one.
From the English, there's no way to know if it is singular or plural. So, they should not say "kamu" or "anda" is incorrect.