Slope of the straight line obtained by plotting $\log_{10} k$ against $\frac{1}{T}$ represents which term?

$A$ reaction is catalysed by $X$. Here $X$:

According to the Arrhenius equation, which of the following statements is correct?

The rate constant for a reaction can be increased by $\underline{a}$ the stability of the reactant or by $\underline{b}$ the stability of the transition state. Select the correct choice for $a$ and $b$.

Which plot of $\ln k$ vs $\frac{1}{T}$ is consistent with the Arrhenius equation?

In the presence of a catalyst,the heat evolved or absorbed during the reaction . . . . . . .