Question

you have been injured in the laboratory (cut, burned, etc.). first you should... ha sido lesionado en el laboratorio (cortes, quemaduras, etc.). primero deberías
see a doctor after school/ ver a una doctora después de la escuela
apply first aid yourself/ aplica los primeros auxilios tú mismo
visit the school nurse after class/ visita a la enfermera de la escuela después de clase
tell the teacher at once/ dile a la maestra a la vez

Explanation:

In a laboratory injury situation, the immediate and most appropriate first step is to inform the teacher right away. This is because the teacher can provide guidance, access to proper first - aid resources, or take further necessary actions. Waiting until after school or class to see a doctor or school nurse, or attempting to self - administer first aid without proper supervision in a lab setting is not the correct initial response.

Answer:

D. tell the teacher at once/ Dile a la maestra a la vez