Correct Answer  Option 2 : Decrease
CONCEPT:
Linear charge density:
 It is defined as the quantity of charge per unit length.
 Its SI unit is C/m.
 If ΔQ charge is contained in the line element Δl, the linear charge density λ will be,
\(\Rightarrow \lambda=\frac{\Delta Q}{\Delta l}\)
Surface charge density:
 It is defined as the quantity of charge per unit area.
 Its SI unit is C/m2.
 If ΔQ charge is contained in the elemental area Δs, the surface charge density σ will be,
\(\Rightarrow \sigma=\frac{\Delta Q}{\Delta s}\)
Volume charge density:
 It is defined as the quantity of charge per unit volume.
 Its SI unit is C/m3.
 If ΔQ charge is contained in the elemental volume Δv, the volume charge density ρ will be,
\(\Rightarrow \rho=\frac{\Delta Q}{\Delta v}\)
EXPLANATION:

Negative charge: A body having an excess of electrons.
 We know that when electrons are added to a positively charged body, the magnitude of the charge on the body decreases.

Surface charge density is defined as the quantity of charge per unit area.
If ΔQ charge is contained in the elemental area Δs, the surface charge density σ will be,
\(\Rightarrow \sigma=\frac{\Delta Q}{\Delta s}\)
 When some electrons are added to a positively charged conducting cone, the total charge on the cone will decrease so the surface charge density also decreases. Hence, option 2 is correct.
Electric Charge
 It is defined as the intrinsic property of certain fundamental particles like electrons, proton, etc, due to which they produce electric and magnetic effects.
 Types of electric charge

Positive charge: A body having a deficiency of electrons.

Negative charge: A body having an excess of electrons.
 Properties of electric charge
 Like charges repel and unlike charges attract each other.
 A charge is a scalar quantity.
 If a system contains a number of point charges, then the total charge of the system is obtained simply by adding all the charges algebraically.
 A charge is always quantized.
 A charge will always remain conserved.
 A charge is always associated with mass.
 The unit of charge is the coulomb.