Which of the following metals releases hydrogen gas upon reaction with cold dilute $HNO_3$?

If $x > 0, y > 0, z > 0, xy + yz + zx < 1$ and if $\tan^{-1} x + \tan^{-1} y + \tan^{-1} z = \pi$,then $x + y + z$ equals to

Identify the plant and structure marked $A$ and $B:-$

Leaching of $Ag_2S$ is carried out by heating it with a dilute solution of

An electron collides with an atom in its ground state at rest. The atom then emits a photon of energy $E_{photon}$. In this process,the change $\Delta E_{elec}$ in the electron's energy 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