Which part of the world has a high density of organisms?

$A$ magnetized wire of magnetic moment $M$ and length $L$ is bent into an arc of a circle subtending an angle of $60^{\circ}$ at the center. The new magnetic moment is:

The figure shows a system of logic gates. From the study of the truth table, it can be found that to produce a high output $(1)$ at $R$, we must have

$A$ circle $C_1$ of radius $2$ touches both $x$-axis and $y$-axis. Another circle $C_2$ whose radius is greater than $2$ touches circle $C_1$ and both the axes. Then the radius of circle $C_2$ is-

Ectophloic siphonostele is found in ...........

How many major groups have recent researchers classified the plant kingdom into?