Final answer:
The grammatical error in the sentence is a 'misplaced modifier,' which occurs when a modifier is improperly separated from the word it describes, leading to potential confusion. Therefore, the correct option in the final answer is c) Misplaced Modifier.
Step-by-step explanation:
The sentence provided contains a misplaced modifier. A misplaced modifier is a word, phrase, or clause that is improperly separated from the word it modifies or describes.
In the sentence 'Unfortunately, the mangroves that protect our coastlines are slowly being uprooted and replaced with beachfront properties,' the adverb 'unfortunately' is meant to express the speaker's attitude towards the entire situation described, but its placement at the beginning of the sentence could mislead a reader to think it modifies only the mangroves.
To clarify the intended meaning, the sentence could be rewritten as: 'It is unfortunate that the mangroves protecting our coastlines are slowly being uprooted and replaced with beachfront properties.'