Cho \(f\left( x \right) = a{x^2} + bx + c\,\left( {a \ne 0} \right)\). Điều kiện để là

A. \(\left\{ \begin{array}{l} a > 0\\ \Delta \le 0 \end{array} \right.\)

B. \(\left\{ \begin{array}{l} a > 0\\ \Delta \ge 0 \end{array} \right.\)

C. \(\left\{ \begin{array}{l} a > 0\\ \Delta < 0 \end{array} \right.\)

D. \(\left\{ \begin{array}{l} a < 0\\ \Delta > 0 \end{array} \right.\)