Sure, here are the sentences completed with the correct forms of "be" and "do":

1. Excuse me, **do** you speak English?
2. Where's Kate? I **don't** know.
3. What's funny? Why **are** you laughing?
4. What **does** your sister do? She's a dentist.
5. It **is** raining. I **don't** want to go out in the rain.
6. Where **do** you come from? Canada.
7. How much **does** it cost to send a letter to Canada?
8. Steve is a good tennis player, but he **doesn't** play very often.