The degree of a polynomial is the highest power of its terms.
The power of a term is the sum of the powers of all the variables in a term.
A polynomial is written starting with the greatest power in standard form.
In the first case, the power of the first term is 3, the power of the second is 3 (2 from x + 1 from y) but the power of x has decreased so it is the second term, and then so on.
In the second case, the power is starting form 2 and then increasing to 3. This is incorrect.
Therefore, Marcus' suggestion is correct.
The period of a sinusoid

is

, so any range such that

will give two complete periods.
Correct me if I’m wrong but I believe it is C
I’m pretty sure it’s A but it could also me C
Hopes it right.