Answer:
make.
Step-by-step explanation:
A verb is one of the parts of speech in English language. Verbs can be defined as any word that describes an action, occurrence, or state of existence. Some examples of verb are dance, sing, walk, play, run, sit, make, etc.
In this scenario, the most appropriate word to fill in the blank space is the verb; make. Make simply means to effect a thing or event by performing an action. Thus, the speaker is advising you to make a reservation because the hotels close to the beach are very popular and get fully booked during the summer.