in domain problems here is two things to keep in mind:
1. Square root or the root of any even power cannot be negative. Also look for things like x^1/4 since that is just the 4th root of x.
2. Denominator cannot be 0.
For such problems you can try plugging the numbers in and see which one of them lead to the 2 points mentioned above, and use elimination by glance to select the options that make more sense to plug in first.
