[" 6.Let "g(x)" be an antiderivative for "f(x)" .Then "ln(1+(g(x))^(2))" is an antiderivative for "],[[" (A) "(2f(x)g(x))/(1+(f(x))^(2))," (B) "(2f(x)g(x))/(1+(g(x))^(2))," (C) "(2f(x))/(1+(f(x))^(2))," (D) none "]]