Final answer:
The correct spelling among the provided options is A. 'Accidently.' It is crucial to verify spellings against a dictionary and not rely solely on spell check applications.
Step-by-step explanation:
Among the options provided, the correctly spelled word is A. Accidently. This is the conventional spelling in American English for the adverb form of 'accidental.' It is important to remember that even reliable spell check applications can sometimes fail to catch incorrect spellings, so cross-referencing with a dictionary is a good habit. A helpful tip to avoid spelling errors is to first consider if you are using the right word for your idea, then to double-check that you have spelled it according to your knowledge.