他接电话时总是先热情地说“你好”。

He always says a cheerful ___hello when answering the phone.

喂！你的钥匙掉在地上了。

___Hello! You dropped your keys on the floor.

我刚加入聊天室，先发个hello打个招呼。

I just joined the chat room and sent a quick ___hello to say hi.