The correct answer is Option D: shake allowance.

In sand casting, the pattern is used to create the mold cavity into which molten metal will be poured. However, simply removing the pattern from the mold can be challenging due to the tight fit between the pattern and the mold. To facilitate easy withdrawal without damaging the mold, certain allowances, known as shake allowances or draft allowances, are provided.

Here's a brief explanation of the different types of allowances:

1. Finishing Allowance: This allowance accounts for the extra material that will be machined away to achieve the final dimensions and surface finish of the cast part.

2. Shrinkage Allowance: This allowance compensates for the contraction of the metal as it cools and solidifies. The pattern is made slightly larger than the final casting to account for this shrinkage.

3. Distortion Allowance: This allowance is for the potential warping or distortion of the casting due to uneven cooling or internal stresses.

4. Shake Allowance: Also known as draft allowance, this is a slight taper or angle added to the vertical surfaces of the pattern to enable easy removal from the mold without damaging the mold cavity.

Therefore, the shake allowance is specifically designed to aid in the removal of the pattern from the sand mold, making Option D the correct choice.