Answer: Make sure arrangement allows each student to see whole-class presentations.
Step-by-step explanation:
The four basic principles of classroom arrangement include:
• The teacher should be able to see all the students.
• decrease obstruction in the high traffic parts of the classroom
• Easy access to commonly used educational materials.
• Make sure that every student is able to see “everything” from where they are seated.
In this case, the basic principles of classroom arrangement that he has forgotten is "making sure arrangement allows each student to see whole-class presentations".