Which of the following is the strongest acid?

If the best and the worst paper never appear together,then in how many ways can six examination papers be arranged?

Which substance of biological origin is used to maintain and increase soil fertility?

Two photons of energies twice and thrice the work function of a metal are incident on the metal surface. Then,the ratio of maximum velocities of the photoelectrons emitted in the two cases respectively,is

If the circles $x^2+y^2-2 \lambda x-2 y-7=0$ and $3(x^2+y^2)-8 x+29 y=0$ are orthogonal,then $\lambda$ is equal to

Match the following genes of the $Lac$ operon with their respective products.
Select the correct option.

$(a)$ $i$ gene	$(i)$ $\beta$-galactosidase
$(b)$ $z$ gene	$(ii)$ Permease
$(c)$ $a$ gene	$(iii)$ Repressor
$(d)$ $y$ gene	$(iv)$ Transacetylase