Complete the sentences with the verbs in brakets.Use gerunds or infinitives. ( v-ing , to verb , verb ) 12. We stand up (greet- chào) .................................. our teachers . 13. We were so happy ...................................(know) from you. 14. I look forward to ............................. ( hear) from you. 15. Let's (play)................................ volleyball together! Các bạn giúp mình với mình cảm ơn