Fill in the gap with "a", "an", "some" or "any". There is ______ orange on the plate.

The sentence is a statement about the existence of an orange on the plate. Since 'orange' is a singular countable noun and starts with a vowel sound, the indefinite article 'an' is appropriate. If the intention was to indicate an unspecified quantity of oranges, 'some' would be used. However, 'an' fits the singular form best. 'Any' is typically used in negative sentences or questions. Therefore, 'an' is the most suitable choice for a simple affirmative statement with a singular noun.

There is an orange on the plate.