Which of the following is different from the other three oxides?

The mass of the earth is $81$ times that of the moon and the radius of the earth is $3.5$ times that of the moon. The ratio of the escape velocity on the surface of the earth to that on the surface of the moon will be:

The extent of charge of a lead accumulator is determined by

The diagram shows a venturimeter through which water is flowing. The speed of water at $X$ is $2\,cm/s$. The speed of water at $Y$ (taking $g = 1000\,cm/s^2$) is ........ $cm/s$.

Which of the following oxides of nitrogen is a blue solid?

What causes a decrease in soil fertility?