Which of the following compounds is not an antacid?

If $L: ax + by + c = 0$ is a variable straight line,where $a, b$ and $c$ are the second,fourth and seventh terms of an $AP$ respectively,then $L$ passes through the fixed point -

The solution of $\frac{dy}{dx} = (\frac{x}{y})^{-1/3}$ is

When light of wavelength $\lambda$ is incident on a photosensitive surface,the stopping potential is $V$. When light of wavelength $3 \lambda$ is incident on the same surface,the stopping potential is $\frac{V}{6}$. The threshold wavelength for the surface is:

If $p \Rightarrow (q \vee r)$ is false,then the truth values of $p, q, r$ are respectively:

Which one of the following removes temporary hardness of water?