8.cost
9.goes
10.listen

8. Those shoes (cost/ costs) too much.
9. My sister (go/goes) to the library once a week.
10. We both (listen/ listens) to the radio in the morning.

8.cost 9.goes 10.listen

8. Those shoes cost too much
⇒ Those shoes là N số nhiều nên ĐT ko chia

9. My sister goes to the library once a week.
⇒ My sister là N số it nên ĐT chia 

10. We both listen to the radio in the morning.
⇒ We là S nhiều nên ĐT ko chia

@Lee Suu - Rin