Option d: copper.
Because copper is an element, not a mixture.
Explanation:
(a) Equilibrium constant expression is ratio of concentrations of products over reactants each raised to their power of stoichiometric coefficients.
For example consider an equilibrium which is:

The expression is:
![K_c=\frac {[C]^c[D]^d}{[A]^a[B]^b}](https://tex.z-dn.net/?f=K_c%3D%5Cfrac%20%7B%5BC%5D%5Ec%5BD%5D%5Ed%7D%7B%5BA%5D%5Ea%5BB%5D%5Eb%7D)
(b) Equilibrium constant of the chemical reaction is value of the reaction quotient of the reaction at the stage of chemical equilibrium which is a state that is approached by the dynamic chemical system at which the composition of the reactant and the product has no measurable tendency towards the change.
(c) Absorbance is the measure of capacity of the substance to absorb the light of a specific wavelength. Absorbance is equal to the logarithm of reciprocal of transmittance.
(d) The Beer's law relates attenuation of the light to properties of material through which light is travelling.
The expression for the law is:
A = ε × l× c
Where,
A is the absorbance
ε is molar absorptivity coefficient
l is the path length
c is the concentration.
Yes, it is a liquid because a solid is a state of matter with a fixed volume and shape; and Gases take both the shape and the volume of their container; and liquid is the one that takes the shape of their container but not necessarily the volume.
The bond angle in H2Se would be predicted should be less than 109.5 degrees. Particle shapes can be anticipated in light of Lewis dab structure utilizing the VSEPR hypothesis. VSEPR remains for Valence Shell Electron Pair Repulsion. It expresses that electron matches in the valence shell of a particle repulse each other; their sub-atomic geometry is the consequence of this shock.