Which one of the following elements on doping with germanium,makes it a $p$-type semiconductor?

$H^{+}$,$D^{+}$,and $T^{+}$ differ in all of the following $EXCEPT$ one. Identify it.

The two enantiomers of secondary butyl chloride differ from each other in which one of the following properties?

The cell reaction $Mn + 2Ag_{(C_1)}^{+} (aq) \to Mn_{(C_2)}^{+2} (aq) + 2Ag$ is represented by

Two capillaries of the same material but of different radii are dipped in a liquid. In one of the capillaries,the liquid rises to a height of $22 \ cm$ and in the other to $66 \ cm$. The ratio of their radii is

The condition for the lines $lx + my + n = 0$ and $l_1x + m_1y + n_1 = 0$ to be conjugate with respect to the circle $x^2 + y^2 = r^2$ is