Fuller's Maximum Density Criterion:
Fuller's maximum density criterion is a method used to determine the maximum density of a soil sample based on the particle size distribution. It states that the maximum density occurs when the particles are arranged in a way that fills the available void space with minimum air voids.

Given Information:
- Maximum size of soil particles = 4 mm

Analysis:
To determine the percentage of particles between 4 mm and 2 mm, we need to understand the particle size distribution and how it relates to Fuller's maximum density criterion.

According to Fuller's criterion, the ideal particle size distribution is achieved when the particles are evenly distributed and fill the available void space with minimum air voids. This means that the particle size distribution should have a continuous gradation from the largest particles to the smallest particles.

In this case, the maximum size of soil particles is given as 4 mm. This means that the particles larger than 4 mm are not considered in the particle size distribution.

Calculation:
To calculate the percentage of particles between 4 mm and 2 mm, we need to determine the fraction of the total weight of soil particles that fall within this size range.

Assuming that the particle size distribution follows a continuous gradation, we can calculate the percentage as follows:

Percentage of particles between 4 mm and 2 mm = (Weight of particles between 4 mm and 2 mm / Total weight of soil particles) * 100

Since the maximum size of soil particles is given as 4 mm, the weight of particles between 4 mm and 2 mm is the same as the weight of particles with a size less than or equal to 4 mm.

Therefore, the percentage of particles between 4 mm and 2 mm can be calculated as:

Percentage of particles between 4 mm and 2 mm = (Weight of particles with a size less than or equal to 4 mm / Total weight of soil particles) * 100

Conclusion:
The correct answer is option C) 30%.