In which of the following,ortho/para substitution by an electrophile is very facile?

Identify the organism shown in the given figure.

The number of subsets of $\{1, 2, 3, \ldots, 9\}$ containing at least one odd number is

$A$ 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

The lanthanide contraction is responsible for the fact that

Which of the following concentration factors is affected by a change in temperature?