Answer: The form of "ser" that completes the sentence provided is "es".
Explanation: The sentence provided can be translated as "Javier ____ student". Therefore,<u> as the sentence is referring to a permanent state, the verb that fills in the blank is "ser".</u> At the same time,<u> "ser" needs to be conjugated into the third person singular because the subject is "Javier", </u>which can be replaced with the third person pronoun "he". <u>The third person singular of the verb "ser" is "es"</u>. Therefore, the form of "ser" that fills in the blank is "es".
As a spanish speaker, I believe it is
a. Es buena idea que hagas una reservación.
