Introduction:
In structural engineering, a column is a compression member that is used to support vertical loads. It is an essential component of many structures, such as buildings and bridges. The effective length of a column refers to the distance between its points of lateral support, where it is prevented from buckling. The effective length is a critical parameter in determining the stability of the column.

Explanation:
The effective length of a column is influenced by various factors, including the material properties, cross-sectional shape, and boundary conditions. The least lateral dimension of a column refers to the smallest dimension of its cross-section, such as the diameter of a circular column or the width of a rectangular column.

To prevent buckling, the effective length of a column should be limited. The most common approach is to limit the effective length to a certain multiple of the least lateral dimension. The correct answer to the given question is option 'C', which states that the effective length should not exceed three times the least lateral dimension.

Reasoning:
The reason behind this limitation is to ensure that the column remains stable under compressive loads. When a column is subjected to a compressive load, it may buckle due to the lateral deflection caused by the load. Buckling refers to the sudden lateral deformation or bending of the column, which can result in its failure.

By limiting the effective length of the column to three times the least lateral dimension, the risk of buckling is significantly reduced. This limitation ensures that the column has adequate lateral support to prevent buckling and maintain its stability.

Alternative Options:
Let's consider the other options provided in the question and understand why they are not correct:

- Option 'A' states that the effective length should not exceed two times the least lateral dimension. This limitation may not provide sufficient lateral support to the column, increasing the risk of buckling.

- Option 'B' suggests that the effective length should not exceed 2.5 times the least lateral dimension. While this limitation is better than option 'A', it may still not provide enough lateral support in some cases.

- Option 'D' proposes that the effective length should not exceed 1.5 times the least lateral dimension. This limitation is too conservative and may unnecessarily restrict the design of columns, leading to inefficient and uneconomical structures.

Therefore, option 'C' is the most appropriate choice as it strikes a balance between providing adequate lateral support and allowing for efficient column design.

Conclusion:
In summary, the effective length of a column should not exceed three times the least lateral dimension to ensure its stability and prevent buckling. This limitation is based on engineering principles and considerations for the safe design of compression members. By adhering to this guideline, structural engineers can design columns that can safely resist compressive loads and maintain the structural integrity of the overall system.