The correct answer is: A. A uniform soil has more strength and stability than a non-uniform soil.
A uniform soil has a narrow range of particle sizes, while a non-uniform soil has a wide range of particle sizes. The smaller the range of particle sizes, the more closely the soil particles can fit together, which results in a stronger and more stable soil.
Option B is incorrect because a uniform soil has more strength and stability than a non-uniform soil.
Option C is incorrect because uniformity coefficient does affect strength and stability.
Option D is incorrect because the uniformity coefficient of a poorly graded soil is less than that of a well graded soil.