To find the difference of the given expression, first step is to get rid of parenthesis. So, distribute negative sign to each terms of the second parenthesis. Hence,
(9x² + 10x + 4) - (9x² + 5x - 1)
= 9x² + 10x + 4 - 9x² - 5x + 1.
= (9x² - 9x²) +(10x - 5x) + (4 + 1) Group the like terms.
= 0 + 5x + 5 Combine the like terms.
= 5x + 5.
So, first choice is correct.
Hope this helps you!