$$ {a^2-b^2-2bc-c^2} over{a^2+b^2+2ab-c^2}$$ is equal to

• A. $$ {a-b-c} over{a+b-c}$$
• B. $$ {a-b+c} over{a+b-c}$$
• C. $$ {a-b-c} over{a+b+c}$$
• D. $$ {a-b-c} over{a+b-c}$$