Which element among the alkaline earth metals primarily forms covalent compounds?

Which one of the following elements in plants is not remobilised?

Which of the following statements is/are incorrect?

An electron (mass = $9.1 \times 10^{-31} \ kg$; charge = $1.6 \times 10^{-19} \ C$) experiences no deflection if subjected to an electric field of $3.2 \times 10^5 \ V/m$ and a magnetic field of $2.0 \times 10^{-3} \ Wb/m^2$. Both the fields are normal to the path of the electron and to each other. If the electric field is removed,then the electron will revolve in an orbit of radius.......$m$

Two rain drops reach the earth with different terminal velocities having ratio $9:4$. Then the ratio of their volumes is

$\frac{{\sqrt{2} - \sin \alpha - \cos \alpha }}{{\sin \alpha - \cos \alpha }} = $