Bonsoir, aidez moi à faire cet exercice svp, merci ​

Bonsoir,
1.a. No, i have to look after my sister
b.I’m coming along absolutely
2.a. Sure! I’ll come
b. Sorry, I can’t
3. It’s fantastic!
4.a.No, I can’t I have to finish my homework
b. Of course, I want!