Identify substrate ' $A$ ' in the following reaction.

$\mathrm{A}+\mathrm{CO}_2 \xrightarrow[6 \text { atm }]{398 \mathrm{~K}}$ Sodium salicylate $\xrightarrow{\mathrm{H}_3 \mathrm{O}^{+}}$Salicylic acid

If a random variable X follows the Binomial distribution $B(10, \quad p)$ such that $5 \mathrm{P}(\mathrm{X}=0)=\mathrm{P}(\mathrm{X}=1)$, then the value of $\frac{\mathrm{P}(\mathrm{X}=5)}{\mathrm{P}(\mathrm{X}=6)}$ is equal to

A particular solution of $\frac{\mathrm{d} y}{\mathrm{~d} x}=(x+9 y)^2$, when $x=0, y=\frac{1}{27}$ is

$$ \mathop {\lim }\limits_{x \to \infty } \frac{\mathrm{e}^{x^4}-1}{\mathrm{e}^{x^4}+1}= $$