Fill in the blank with an appropriate Preposition.
'I have eaten nothing ______ yesterday'.

The correct answer is Option B (since).

Key Points:
• 'Since' is used with a specific point of time in the past from which an action began and continues into the present (Point of Time).
• 'For' is used for a duration or length of time (Period of Time).
• 'Yesterday' represents a definite starting point of time.
• In the present perfect tense ('have eaten nothing'), 'since' correctly marks the point in time: 'I have eaten nothing since yesterday.'
• Key Takeaway: Use 'since' with a point of time (yesterday, 2 PM) and 'for' with a period of time (two hours).