10 because it's an even number !
1000 does not belong as all of the other numbers are squares and 1000 is a cube. 121 = 112 361 = 192 576 = 242
1 - it is the only number that is neither prime nor composite.
Since the number series are not provided it is hard to know how to continue it. A person would need to see the following series to know the answer.
The numbers that belong to the series are the following: 1, 2, 5, 10, 13, 26, 29 and 48.
Numerical Answer48 does not belong, because the sequence is (double) then (add 3) and after 256 to 29, the last number should be 58.Spelling Answer2 does not belong, because the rest of the numbers include the letter E when you spell them out in English.
You could make a case for any of them.