The first life on Earth was .....

If the line $x+3y=0$ is the tangent at $(0,0)$ to the circle of radius $1$,then the centre of one such circle is

Match the type of elasticity involved:

Process	Elasticity Type
$(i)$ Suspension fibre of galvanometer	$(a)$ Linear
$(ii)$ Bending of beam	$(b)$ Shear
$(iii)$ Cutting piece of paper	$(c)$ Bulk
$(iv)$ Mechanical waves in fluid	$(d)$ Shear

$A$ metal ion involved in stomatal regulation is

If $A$ and $B$ are any two sets,then $(A \cup B)'$ is equal to

$A$ particle of mass $10\, g$ is kept on the surface of a uniform sphere of mass $100\, kg$ and a radius of $10\, cm$. Find the work to be done against the gravitational force between them to take the particle far away from the sphere. (Take $G = 6.67 \times 10^{-11} \, Nm^2/kg^2$)