Which of the following is an acceptable datum identifying letter?

The choice identifying letter must adhere to accepted conventions in various fields, particularly in technical documentation and data management practices. Letters are typically used as identifiers because they are distinct and easy to differentiate, which aids in clarity and comprehension.

In this context, using a letter like "A" is appropriate as it falls within the standard range of alphabetic characters typically designated for labeling and categorizing data points or identifiers. This practice allows for straightforward communication and organization without the potential confusion that could arise from numerical or special character designations.

Other options may not convey the same level of clarity or may be less conventional, which is why they are not suitable as datum identifying letters in this context.