Answer:
The best synonym for "makeshift" in the sentence provided is D. temporary. >:3
Step-by-step explanation:
As was posted, the word "makeshift" has several meanings. In the sentence "The kids wanted to keep the lost dog safe, so they quickly gathered supplies to build a makeshift doghouse," the best meaning for makeshift seems to be temporary. The purpose of the doghouse the children are building is to keep the dog safe. We have no context other than the sentence itself, but let's assume the children will decide how to better help the dog later. The doghouse is just to make sure it has a safe place to stay and sleep. It is temporary, since they are likely to find a better place for the dog to stay.
The other options are close in meaning, but not as good as temporary. Expedient refers to something that is practical, but may be immoral. Provisional refers to something that exists in a certain way or form in the present but might be changed later. I'd say it is the second best option. Finally, slapdash refers to something done carelessly. =^.^=