The real numbers c, b, a form an arithmetic sequence with a \geq b \geq c \geq 0. The quadratic a x^{2}+b x+c has exactly one root. What is this root?

**Answer Choices**

A. -7-4 \sqrt{3}

B. -2-\sqrt{3}

C. -1

D. -2+\sqrt{3}

E. -7+4 \sqrt{3}

The real numbers c, b, a form an arithmetic sequence with a \geq b \geq c \geq 0. The quadratic a x^{2}+b x+c has exactly one root. What is this root?

**Answer Choices**

A. -7-4 \sqrt{3}

B. -2-\sqrt{3}

C. -1

D. -2+\sqrt{3}

E. -7+4 \sqrt{3}