According to Rankine's earth pressure formula for shallow bins, lateral pressure at the base of depth $h$ is $L = k \cdot w \cdot h$, where $L = 6000\text{ kgf/m}^2$, pressure coefficient $k = 0.5$, and bulk density $w = 600\text{ kg/m}^3$. Solving for height: $h = \frac{L}{k \cdot w} = \frac{6000}{0.5 \times 600} = \frac{6000}{300} = 20\text{ m}$. Option analysis: (A) $30\text{ m}$ is incorrect. (B) $20\text{ m}$ is the exact calculated bin height. (C) $10\text{ m}$ is incorrect. (D) $5\text{ m}$ is incorrect.

Janssen's equation for lateral grain pressure is $L = \frac{w R}{\mu'} \left[1 - e^{-\frac{k \mu' y}{R}}\right]$. The variables explicitly influencing lateral pressure $L$ are bulk density of grain $w$ (C), lateral-to-vertical pressure ratio $k$ (A), depth of grain $y$ (D), hydraulic radius of bin $R$, and wall friction coefficient $\mu'$. Individual grain microscopic shape (B) is not an explicit parameter in the formula. Hence (A), (C), and (D) are the factors. Option analysis: (A) Includes grain shape. (B) Omits pressure coefficient. (C) (A), (C) and (D) only is the correct answer. (D) Includes grain shape.