Right Answer:
Escribe
This a sentence written in present tense with the 3rd person singular ella (she), because La profesora is a femenine subject.
Therefore the correct conjugation of the verb escribir (to write) in present tense and indicative mode is (ella) escribe (she writes).
Now the whole sentence is:
La profesora escribe el examen
(The teacher writes the exam)
The other options are incorrect because, although they are in present tense and indicative mode, the conjugation does not match with the subject of the sentence:
(Yo) escribo (I write)
(Tú) escribes (You write)
(Ellos/Ellas) escriben (They write)