To find the conduction current density, we need to use Ohm's law, which states that the current density (J) is equal to the conductivity (σ) times the electric field (E).

Given:
Conductivity (σ) = 200 units
Electric field (E) = 1.5 units

Using the formula J = σ * E, we can calculate the conduction current density.

Calculation:
J = 200 * 1.5
J = 300 units

Hence, the conduction current density is 300 units.

Explanation of the solution:

1. Ohm's Law:
Ohm's law relates the current density (J) in a material to the conductivity (σ) and electric field (E) applied to it. It is given by the equation J = σ * E, where J is in units of current per unit area, σ is in units of conductivity, and E is in units of electric field.

2. Conductivity:
The conductivity (σ) of a material determines how well it conducts electric current. It is a measure of the material's ability to allow the flow of electric charges. The higher the conductivity, the better the material conducts current.

3. Electric Field:
An electric field (E) is created by a voltage difference between two points in a material. It exerts a force on charged particles, causing them to move and create an electric current. The strength of the electric field determines the rate at which charges flow through the material.

4. Conduction Current Density:
The conduction current density (J) is a measure of the amount of electric current flowing through a unit area of a material. It represents the flow of charged particles (usually electrons) within the material due to the applied electric field.

5. Calculation:
To find the conduction current density, we multiply the conductivity (σ) by the electric field (E) using the formula J = σ * E. Plugging in the given values, we get J = 200 * 1.5 = 300 units.

Therefore, the correct answer is option 'D' (300).