Final answer:
Option (A), The preposition in the sentence is 'toward,' which shows the direction to find the lemon grove.
Step-by-step explanation:
The word 'toward' in the sentence 'Head toward the large yellow sign to find the lemon grove' is a preposition. Prepositions are words that indicate direction, location, or time and show the relationship between the noun or pronoun and other parts of a sentence. In this case, 'toward' is showing the direction in which to head to find the lemon grove.