"What are you doing?"
Translation:तुम क्या कर रही हो ?
From Indian I also heard "आप क्या कर रहे हो " - is this colloquial?
If it marks कर रही हो as correct, shouldn't it mark कर रहा हो as correct as well?
No. Since तुम is grammatically considered plural (even though it can indicate a single individual or multiple people. The same goes for आप ), it wil always be रहे when masculine.
Isn't "कर" work? Doesn't "तुम क्या कर रही हो" translate as "what do you do for work" rather than "what are you doing?"
Whenever raha/rahi gets involved, you can be sure of it being a continuous sentence. In other words "ing" will definitely be involved in the English counterpart of that sentence.
What do you do - Tum kya karti/karte ho.
What do you do for work - Tum kya kaam karti/karte ho.
No, काम means work.
कर is the verb stem of करना, which means to do. कर रहा/रही is the present continuous form of करना. Therefore, कर रही/रहा means doing.
"तुम क्या काम करते/करती हो?" would be "what work do you do".
As countinous form I think it should actually be "What work are you doing" or "What are you working".