Answer:
tiene
Step-by-step explanation:
Our verb is "tener", so we need to conjugate it accordingly.
"Tener" is a bit of an irregular verb: its "yo" form is very different from its other forms, and it's an "e" to "ie" verb (we change all the first "e's" to "ie's"). So, the conjugations and their respective subjects are:
yo tengo
tú tienes
él/ella/usted tiene
nosotros tenemos
ellos/ellas/ustedes tienen
The subject here is "el maestro", which refers to "the teacher". Because this is a singular subject, we use the él/ella/usted form of "tener", which would be tiene.