English grammar error-spotting (correct prepositions with dates and clock time): Read the sentence in four parts (A–D) and choose the part containing any grammatical error; if all parts are correct, pick ‘‘No error.’’ Focus on prepositional phrases for appointments: ‘‘I have / an appointment / on the 9th September on five o'clock / No error.’’

Given data

• A: ‘‘I have’’
• B: ‘‘an appointment’’
• C: ‘‘on the 9th September on five o'clock’’
• D: ‘‘No error.’’

Concept / Approach
Use on with dates, usually ‘‘on the 9th of September’’, and use at with clock times (‘‘at five o'clock’’). Two preposition errors occur in Part C.

Step-by-step evaluation
Step 1: Date phrase → ‘‘on the 9th of September’’.Step 2: Time phrase → ‘‘at five o'clock’’.Step 3: Hence, Part C is erroneous: ‘‘on the 9th September on five o'clock’’.

Correction
‘‘I have an appointment on the 9th of September at five o'clock.’’

Common pitfalls

• Using ‘‘on’’ before clock times.
• Omitting ‘‘of’’ in full date expressions.

Final Answer
on the 9th September on five o'clock