For the function f(x) =ln(x²+36) , where is the function concave upward and where is it concave downward?
A. Concave upward: (6,[infinity]) ; Concave downward: (−6,6)
B. Concave upward: (−6,6) ; Concave downward: (−[infinity],−6) ∪(6,[infinity])
C. Concave upward: (−[infinity],−6) ∪(6,[infinity]) ; Concave downward: (6,[infinity])
D. Concave upward: (−[infinity],−6) ∪(6,[infinity]) ; Concave downward: (−6,6)