根据句意，用括号中所给单词的适当形式完成句子。
1. Her parents are out. She's _______ (babysit) her sister.
2. Tom _______ (can) come to my party because he is ill.
3. Thank you for your _______ (invite) to your party.
4. Please keep quiet!My sister's trying _______ (study).
5. He would love _______ (have) a cup of tea.
