In which plant was the importance of day length for flowering first observed?

Factors affecting the Hardy-Weinberg principle are:
$(I)$ Gene flow
$(II)$ Genetic drift
$(III)$ Mutation
$(IV)$ Genetic recombination
$(V)$ Natural selection
The correct combination is:

Which of the following groups of cells in the male gonad represents haploid cells?

Which of the following is a dihydric alcohol?

$A$ deflection magnetometer is adjusted and a magnet of magnetic moment $M$ is placed on it in the usual manner and the observed deflection is $\theta$. The period of oscillation of the needle before settling of the deflection is $T$. When the magnet is removed,the period of oscillation of the needle is $T_0$ before settling to $0^{\circ}-0^{\circ}$. If the earth's horizontal magnetic field is $B_H$,the relation between $T$ and $T_0$ is

If the plane $7x + 11y + 13z = 3003$ meets the coordinate axes at $A, B, C$, then the centroid of the $\triangle ABC$ is