What is the value of slope, if $\log _{10} \mathrm{~K}$ (y-axis) is plotted versus $1 / \mathrm{T}$ ( $x$-axis) for Arrhenius equation?

Identify a compound having highest thermal stability.

Which among the following has highest basic strength?

Identify the nitrogen atom of purine base that bonds with $1^{\prime}$ carbon of ribose to form ribonucleoside?