Explanation:
well, what does the word "constant" tell you ?
e.g. "this is a constant reminder of ..."
a constant is steady and unchanging. always the same.
so, what could be the constant part/term in the expression ?
-3xy ? is that always the same value ? no matter what values you assign to x, y (and whatever other variables there might be in the system)?
or
10 ? is that always the same value, no matter what values are assigned to x, y, ... ?
there are no other parts/terms I can see here.
so, please use your common sense and pick the right one. you can do that !
this is so simple. to outright write the answer to this feels like an offense. also against your own intelligence.