Which of the following is known as the $ \text{Christmas Tree} $?

$A$ magnetized wire of magnetic moment $M$ and length $l$ is bent into the form of a semicircle of radius $r$. Then its new magnetic moment is:

Two thin lenses of focal lengths $f_1$ and $f_2$ are in contact and coaxial. The power of the combination is

$Ge$ and $Si$ diodes conduct at $0.3 \ V$ and $0.7 \ V$ respectively. In the following figure,if the $Ge$ and $Si$ diode connections are reversed,the value of $V_0$ changes by .....$V$.

The area of the region bounded by the curve $y=2x-x^2$ and the $X$-axis is

Which of the following is $NOT$ a characteristic of Phylum $Annelida$?