Which of the following halides has the maximum melting point?

$A$ solid cylinder of mass $M$ and radius $R$ rolls without slipping down an inclined plane of length $L$ and height $h$. What is the speed of its centre of mass when the cylinder reaches its bottom?

Which one of the following elements reduces $NaOH$ to $Na$?

Which of the following statements is correct?

Velocity of sound waves in air is $330 \ m/s$. For a particular sound wave in air,a path difference of $40 \ cm$ is equivalent to a phase difference of $1.6 \pi$. The frequency of this wave is: (in $Hz$)

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