Let $a, b$ be non-zero real numbers. Which of the following statements about the quadratic equation $a x^{2}+(a+b) x+b=0$ is neccesarily true? $(\mathrm{I})$ It has at least one negative root $(\mathrm{II})$ It has at least one positive root. $(\mathrm{III})$ Both its roots are real.

• A

  $(\mathrm{I})$ and $(\mathrm{II})$ only
• Correct answer
  B

  $(\mathrm{I})$ and $(\mathrm{III})$ only
• C

  $(\mathrm{II})$ and $(\mathrm{III})$ only
• D

  All of them

Hence, the correct answer is option: 'B'.