Which of the following graphs of a quadratic function satisfies the condition given below?
a < 0; b² - 4ac = 0

Graph of a quadratic function opening downwards with vertex at (0, 0).

Graph of a quadratic function opening upwards with vertex at (0, 5).

Graph of a quadratic function opening upwards with vertex at (0, -5).

Graph of a quadratic function opening downwards with vertex at (0, -5).

Which of the following graphs of a quadratic function satisfies the condition given below?a < 0; b2 - 4ac = 0