This question asks to identify the grammatically incorrect part of the sentence: "The old man fell down from the stairs." Let's break down the sentence and analyze each part.

Analyzing Sentence Components

• 4. The old man: This part serves as the subject of the sentence. It correctly identifies who performed the action.
• 3. fell down: This is the verb phrase. 'Fell' is the past tense of 'fall'. While 'fall' implies downward movement, 'fell down' is commonly used, although sometimes considered redundant. It emphasizes the downward motion and is generally acceptable in most contexts.
• 1. from the stairs: This is a prepositional phrase indicating location or origin.
• 2. No error: This option suggests the sentence is perfectly correct as is.
• 5. This option is empty and doesn't represent a part of the sentence.

Identifying the Grammatical Error

The core issue lies in the prepositional phrase "from the stairs". In English, when describing someone falling off a raised surface like stairs, the correct preposition is typically 'off' or 'down'.

• Correct Usage 1: "The old man fell off the stairs." This implies he lost his balance and fell from the surface of the stairs.
• Correct Usage 2: "The old man fell down the stairs." This emphasizes the movement along the stairs in a downward direction.

Using 'from' suggests the origin or source of the fall, which doesn't fit the context of falling *on* or *along* the stairs. Therefore, "from the stairs" is the incorrect part.

Conclusion on Sentence Structure

The sentence "The old man fell down from the stairs" contains a prepositional error. The most appropriate phrasing would be "The old man fell off the stairs" or "The old man fell down the stairs." Based on this analysis, the incorrect part is "from the stairs".