Which of the following is a favourable factor for cation formation?

If the lines $4x + 3y - 1 = 0$,$x - y + 5 = 0$,and $kx + 5y - 3 = 0$ are concurrent,then $k$ is equal to:

Select the correct statement from the ones given below:

The nucleus of an element contains $9$ protons. Its valency would be

$A$ particle of mass $200\,g$ executes a simple harmonic motion. The restoring force is provided by a spring of spring constant $80\,N/m$. The time period is .... $sec$.

In the stomach,gastric acid is secreted by the