Final answer:
The medulla oblongata is part of the brainstem with vital functions and is approximately 2.5 cm in length, corresponding with option A as the answer.
Step-by-step explanation:
The medulla oblongata is a crucial part of the human brain that facilitates a number of automatic functions, such as breathing and heart rate regulation. It is part of the brainstem and connects the higher levels of the brain to the spinal cord. When it comes to its size, it is approximately 2.5 cm in length. This measurement corresponds with option A. It is understandable that there could be some variation in measurement, as mentioned in the reference text, where a tenth of a centimeter could be uncertain. However, within a common reference range, 2.5 cm is considered an accurate estimate for the length of the medulla oblongata.