Chitin is an example of which of the following?

$A$ and $B$ are two radioactive substances whose half-lives are $1$ and $2$ years respectively. Initially, $10 \, g$ of $A$ and $1 \, g$ of $B$ are taken. The time (approximate) after which they will have the same quantity remaining is ........... $years$.

The more commonly used baking powder contains about $30 \% NaHCO_3, 20 \% NaAl(SO_4)_2, 10 \% Ca(H_2PO_4)_2$ and $40 \% $ starch. Which of the following statements is/are correct?

The offspring produced from the cross between two pure parents are more vigorous and high-yielding. What is this phenomenon called?

Considering only the principal values of inverse functions,the set $A = \{x \geq 0, \tan^{-1}(2x) + \tan^{-1}(3x) = \frac{\pi}{4}\}$

If the normal to the curve $y = f(x)$ at the point $(3, 4)$ makes an angle $\frac{3\pi}{4}$ with the positive $x$-axis,then $f'(3)$ is equal to