ANS:D - all the above.

In a cantilever retaining wall without a heel slab, the design considerations for the stem and the base slab are crucial for ensuring stability and structural integrity. Let's analyze each option provided:

1. Thickness of the stem is kept same throughout: This option suggests that the thickness of the stem remains constant along its height. While this approach is feasible and common in many designs, it may not always be the most efficient choice, especially for taller retaining walls where varying thicknesses might be required to optimize material usage and structural performance.
2. Base slab is made 10 cm thicker than the stem: This option involves increasing the thickness of the base slab relative to the stem by a specified amount (10 cm). This approach aims to provide additional stability and bearing capacity to the lower portion of the retaining wall, where the soil pressures are typically higher. It helps distribute the load more effectively and reduce the risk of overturning and sliding.
3. Width of the base slab is kept 0.7 times the total height of the wall: This option suggests a specific ratio between the width of the base slab and the total height of the wall. Keeping the base slab width proportional to the height of the wall helps ensure adequate stability and resistance against overturning forces. However, the specified ratio of 0.7 might vary depending on the specific design requirements and soil conditions.
4. All the above: This option encompasses all the design considerations mentioned above, including maintaining a constant stem thickness, increasing the base slab thickness, and proportioning the base slab width to the total height of the wall.

Considering the comprehensive nature of option 4, "all the above" seems to be the most appropriate choice, as it accounts for various design aspects aimed at enhancing the stability and performance of the cantilever retaining wall without a heel slab. Therefore, the correct option is "all the above."