If $f(0)=0, f(1)=1, f(2)=2$ and $f(x)=f(x-2)+f(x-3)$ for $x=3, 4, 5, \ldots$,then $f(9)$ is equal to

$A$ compound $X$ upon reaction with $H_{2}O$ produces a colorless gas $Y$ with a rotten fish smell. Gas $Y$ is absorbed in a solution of $CuSO_{4}$ to give $Cu_{3}P_{2}$ as one of the products. Predict the compound $X$.

The catalyst used in the contact process is

$A$ point charge $+q$ is placed at the centre of a cube of side $L$. The electric flux emerging from the cube is

The number of significant figures in $23.023$,$0.0003$,and $2.1 \times 10^{-3}$ are respectively:

The eccentricity of the ellipse $\frac{x^2}{16} + \frac{y^2}{9} = 1$ is