The given roots are
$\alpha= i \sqrt 7$
$\eta= -i \sqrt 7$
Sum $ \alpha +\beta=i \sqrt 7 - i \sqrt 7=0$
Product $\alpha \beta = i \sqrt 7 \times i \sqrt 7=0$
$\qquad= -i^2 7 =7$
The quadratic equation whose roots are $\alpha , \beta$ is
$x^2$-(sum of the roots)x+product of the roots=0$
$x^2-(\alpha+\beta)x +\alpha \beta=0$
$x^2-ox+7=0$
$x^2+7=0$
Hence 1 is the correct answer