male

adult

blackboard

teacher

person

one

education

writing

classroom

caucasian

people

intelligence

chalk

university

lecture

hall

science

years

equipment

professor

learning

expertise

symbol

man

instructor

mathematics

serious

human

standing

number

point

book

table

window

clock

formula

inequality

equation

complex

glasses

chair

indoor

inside

quantum

physics

optics

panorama

copy

encircle