Simplify $-2 \sqrt{5}+2 \sqrt{20}$ Select the correct choice below and fill in any answer boxes in your choice. A. $-2 \sqrt{5}+2 \sqrt{20}=\square$ (Simplify your answer. Type an exact answer, using radicals as needed.) B. The expression cannot be simplified.

Step 1 ：The given expression is $-2 \sqrt{5}+2 \sqrt{20}$.

Step 2 ：We can simplify the square root of 20 to 2 times the square root of 5, so the expression becomes $-2 \sqrt{5}+2*(2 \sqrt{5})$.

Step 3 ：This simplifies to $-2 \sqrt{5}+4 \sqrt{5}$.

Step 4 ：We can combine like terms to get the final answer: $-2 \sqrt{5}+4 \sqrt{5}=\boxed{2\sqrt{5}}$