The idea is that just like tennis the student must practice hitting the "balls" back accurately. Students stand at one end of the room while the teacher stands at the other end, since this exercise is to practice not only using articles ("an," "an," "the") and various speech sounds, but to speak loudly and with confidence.
Teacher (the ball launcher)
(Recycle vocabulary from lessons.)
tennis ball   tennis ball   tennis ball Student (the player)
tennis racket
dog, apple, rabbit, ruler, project, stapler, eraser, tape roll, umbrella, orange jacket, tax refund, savings account, interesting book, economy class ticket, busy schedule, early morning flight, late afternoon meeting
"a" vs. "an"

robot speech vs. linkage/coarticulation
(e.g., I "hava" dog.)
I have a dog.
I have an apple.
cat, orange, deadline, problem, bicycle, veggie burger, fish and chips, anniversary gift, window seat, big paycheck, amazing presentation, party invitation, enormous appetite, electricity bill to pay "a" vs. "an" He has a cat.
He has an orange.
bird, egg, application, boarding pass, uncomfortable seat, evening flight, air conditioner, wall-to-wall carpeting, studio apartment, incredible car "a" vs. "an" She has a bird.
She has an egg.
rabbits /s/, strawberries /z/, dishes /Iz/

doughnuts /s/, status reports /s/, movie tickets /s/, theatre tickets /s/, cigarettes /s/

muffins /z/, French fries /z/, exciting news /z/, other plans /z/, many expenses /Iz/
no article

/s/, /z/, /Iz/ pronunciation
She has rabbits. /s/

She has strawberries. /z/

She has dishes. /Iz/ + extra syllable