在下列各句的空白处填入一个适当的词，使句子意思完整、语法正确。
1. When I saw him, he was walking ________ his school.
2. All the guests arrived at the party but the host didn't ________ up.
3. On Sunday school is usually _________ and students have one day off.
4. Gold is a kind of much-loved _________, so everyone likes it.
5. Yesterday Tom _________ me some money and I return it to him today.
