1. Your answer would be C. 5xy(2y² - 5xy + 3)
This is because you can see that 5xy would be the greatest common factor of all of the terms given, and C is the only option where 5xy is outside of the bracket.
2. The greatest common factor of 16x² - 4x would be 4x, so you'd get 4x(4x - 1) = 0, which leaves your solution as {0, 1/4}, which is answer B.
I hope this helps!