Product $(A)$ is

In which of the following reactions does $H_2O_2$ act as a reducing agent?

$A$ metal $M$ readily forms its sulphate $MSO_4$,which is water soluble. It forms oxide $MO$ which becomes inert on heating. It forms insoluble hydroxide which is soluble in $NaOH$. The metal $M$ is

$A$ wire of length $L$ and $3$ identical cells of negligible internal resistances are connected in series. Due to the current,the temperature of the wire is raised by $\Delta T$ in time $t$. $N$ number of similar cells is now connected in series with a wire of the same material and cross section but of length $2L$. The temperature of the wire is raised by the same amount $\Delta T$ in the same time $t$. The value of $N$ is:

$Ge$ and $Si$ diodes conduct at $0.3 \ V$ and $0.7 \ V$ respectively. In the following figure,if the $Ge$ and $Si$ diode connections are reversed,the value of $V_0$ changes by .....$V$.

What are the shapes of ethyne and methane?