Nylon $2-$ Nylon $6$ is

Which of the following ligands is expected to be bidentate?

The metal ion present in vitamin $B_{12}$ is

Which of the following statements is not true?

The wavelengths of two notes in air are $\frac{36}{195} ~m$ and $\frac{36}{193} ~m$. Each note produces $10$ beats per second separately with a third note of fixed frequency. The velocity of sound in air in $m/s$ is

$(\vec{a} \times \vec{b}) \times [(\vec{b} \times \vec{c}) \times (\vec{a} \times \vec{b} + \vec{b} \times \vec{c} + \vec{c} \times \vec{a})]$ is