In $Anthoceros$,vegetative reproduction occurs by which of the following?

Which of the following is known as a fluid connective tissue?

The number of triangles that can be formed by choosing the vertices from a set of $12$ points,seven of which lie on the same straight line,is

$AB$ is an ionic solid. The ionic radii of $A^{+}$ and $B^{-}$ are respectively $r_c$ and $r_a$. Lattice energy of $AB$ is proportional to :

The atomic numbers of elements $X, Y$ and $Z$ are $19, 21$ and $25$ respectively. The number of electrons present in the $M$-shell of these elements follow the order:

The correct order of the $O-O$ bond length in $O_2, H_2O_2$,and $O_3$ is