What is the technique of obtaining a large number of plantlets by tissue culture called?

If $y = \sec(\tan^{-1} x)$,then $\frac{dy}{dx}$ at $x = 1$ is equal to

Which sugar is represented by the structural formula shown below?

The plant part which consists of two generations,one within the other,is:

If the rate of disappearance of $N_2O_5$ in the following reaction is $1.2 \times 10^{-5} \ mol \ L^{-1} \ s^{-1}$,the rate of production of $NO_2$ in $mol \ L^{-1} \ s^{-1}$ is:
$2 \ N_2O_{5(g)} \longrightarrow 4 \ NO_{2(g)} + O_{2(g)}$

Which phylum is characterized by the presence of a central cavity known as the spongocoel?