Which of the following is optically active?

As shown in the figure,a metal rod makes contact and completes the circuit. The circuit is perpendicular to the magnetic field with $B = 0.15 \, T$. If the resistance is $3 \, \Omega$,the force needed to move the rod as indicated with a constant speed of $2 \, m/s$ is:

In pea plants,yellow seeds are dominant over green seeds. If a heterozygous yellow-seeded plant is crossed with a green-seeded plant,what ratio of yellow to green-seeded plants would you expect in the $F_1$ generation?

Among $Ni(CO)_4$,$[Ni(CN)_4]^{2-}$,and $[Ni(Cl)_4]^{2-}$,which of the following statements is correct regarding their magnetic properties?

If the number average molecular weight and weight average molecular weight of a polymer are $40000$ and $60000$ respectively,the polydispersity index of the polymer will be

The bob of a simple pendulum is hanging vertically down from a fixed identical bob by means of a string of length $l$. If both bobs are charged with a charge $q$ each,what is the time period of the pendulum? (Ignore the radii of the bobs.)