Вставьте нужные модальные глаголы (can, may, must) i take your pen? i invite nick to our house? certainly, you . they understand french. you work hard at your english. i shut the door?

May/Can I take your pen?
May I invite Nick to our house? Certainly, you can.
Theycan understand French.
You must work hard at your English.
May I shut the door?