Identify the grammatical error in the sentence: "Many medical providers (including the local public health clinic) promote four keys to living a healthy life: exercising, healthy diet, a balanced life, and avoid substances like alcohol, drugs, and tobacco."?

The sentence in question has a grammatical inconsistency in its list format, which is why identifying a lack of uniformity in lists makes the most sense as the correct answer. In a series, each item needs to maintain the same grammatical structure for clarity and coherence. Here, three items in the list are presented as nouns or noun phrases ("exercising," "healthy diet," and "a balanced life"), while the fourth item ("avoid substances like alcohol, drugs, and tobacco") is framed as a verb phrase. This inconsistency disrupts the flow and makes the list appear unbalanced.

Ensuring that the items in a list align grammatically enhances readability and comprehension. By adjusting the last item to match the structure of the others – for example, by changing "avoid substances" to "avoiding substances" – the sentence would adhere to a uniform format and improve overall clarity.