To determine the correct preposition to fill in the blank, let's analyze the sentence structure and the meaning of the sentence.
1. The sentence structure: "Sabina has invited his friends ____ dinner."
2. The verb "invited" is followed by the object "his friends", indicating that Sabina has asked his friends to do something.
3. The word "dinner" indicates the activity or event for which Sabina has invited his friends.
Now let's consider the possible prepositions and their meanings:
A. "For" - This preposition is used to indicate the purpose or reason for an action. In this case, it would imply that Sabina has invited his friends for the purpose of having dinner together.
B. "To" - This preposition is used to indicate direction or movement towards a specific location or person. In this case, it would imply that Sabina has invited his friends to come to a dinner event.
C. "With" - This preposition is used to indicate companionship or association. In this case, it would imply that Sabina has invited his friends to join him for dinner.
D. "Over" - This preposition is used to indicate movement from one place to another or a change in location. In this case, it does not fit the context of the sentence.
Based on the analysis above, the correct preposition to fill in the blank is "for" (option A). Sabina has invited his friends for dinner, indicating that the purpose or reason for the invitation is to have dinner together.

Explanation:

Preposition 'for' in this context:
- The correct preposition to use in this sentence is 'for'.
- When we invite someone for something, it means that we are inviting them to participate in or attend an event or activity.

Example:
- Sabina has invited his friends for dinner.
- This sentence indicates that Sabina has asked his friends to join him for a meal or dinner gathering.

Incorrect options:
- Option 'b' (to) is not the correct preposition to use in this context. 'To' is used to indicate direction or movement towards a specific place or person.
- Option 'c' (with) is not the correct preposition to use in this context. 'With' is used to indicate accompaniment or association with someone or something.
- Option 'd' (over) is not the correct preposition to use in this context. 'Over' is often used to indicate movement above or across something.

Therefore, the correct preposition to use in this sentence is 'for', making the correct answer option 'a'.