Final answer:
In the sentence provided, 'decided' is the abstract noun as it refers to the act of making a decision, and 'doctor's office' is the concrete noun as it is a specific place that can be seen and visited. The correct option is b) Abstract noun: decided, Concrete noun: join.
Step-by-step explanation:
The sentence 'Mary decided to join Daniel at the doctor's office' contains both an abstract noun and a concrete noun.
An abstract noun refers to an idea, quality, or state that cannot be seen or touched, while a concrete noun refers to a physical object that can be observed with the senses.
In this sentence, the abstract noun is 'decision,' implied by the word 'decided,' which represents the act of making a decision and is not something that can be touched or seen. The concrete noun is 'doctor's office,' which refers to a specific, tangible place that can be seen and visited.
Therefore, the correct option is b) Abstract noun: decided, Concrete noun: join.