The correct answer is A. to.
The word “assent” means to agree or consent. In this sentence, the father is refusing to agree to his child spending a holiday abroad before they are 6 years old. The preposition “to” is used to indicate the purpose or goal of an action. In this case, the father is refusing to agree to the action of his child spending a holiday abroad.
The other options are incorrect because they do not make sense in the context of the sentence. The preposition “in” is used to indicate a location or position. The preposition “for” is used to indicate a reason or purpose. The preposition “from” is used to indicate a source or origin.
Here are some examples of how the other options could be used in a sentence:
- The child is looking forward to going on holiday in Spain.
- The child is asking for permission to go on holiday for a week.
- The child is coming from a family that loves to travel.