Which of the following elements does not form a monoxide?

If $K_{sp}$ of $CaF_2$ at $25\,^{\circ}C$ is $1.7 \times 10^{-10}$,the combination amongst the following which gives a precipitate of $CaF_2$ is

Gold numbers of protective colloids $A$,$B$,$C$ and $D$ are $0.50$,$0.01$,$0.10$ and $0.005$,respectively. The correct order of their protective powers is

Glycogen is a polymer of

$A$ beaker contains $200\, g$ of water. The heat capacity of the beaker is equal to that of $20\, g$ of water. The initial temperature of water in the beaker is $20^\circ C$. If $440\, g$ of hot water at $92^\circ C$ is poured into it,the final temperature (neglecting radiation loss) will be nearest to $^\circ C$.

The blocks shown in the figure move with a constant velocity of $10 \, m/s$ towards the right. All surfaces in contact are rough. The friction force applied by block $B$ on block $A$ is ........... $N$.