Which of these is least likely to act as a Lewis base?

The integrating factor of the differential equation $(x \log x) \frac{dy}{dx} + y = 2 \log x$ is

Let $\bar{a} = 3 \hat{i} + 2 \hat{j} + x \hat{k}$ and $\bar{b} = \hat{i} - \hat{j} + \hat{k}$,for some real $x$. Then $|\bar{a} \times \bar{b}| = r$ is possible,if

$\lim _{x \rightarrow \infty}\left(\frac{x+6}{x+1}\right)^{x+4}$ is equal to

One of the endangered species of Indian medicinal plants is

Axillary bud and terminal bud are derived from the activity of