Commas with introductory words

Where should the comma be placed? Wow I didn't know you were from Jamaica.

• behind the word "didn't"
• behind the word "from"
• in front of the word "Jamaica
• behind the word "Wow"

Where should the comma be placed? Yes you can have my pizza and wings.

• behind the word "yes"
• behind the word "pizza"
• in front of the word "wings"
• in front of the word can

Where should the comma be placed?

Lastly my mom baked delicious cookies for the bake sale.

• Lastly my mom baked delicious, cookies for the bake sale.

• Lastly my mom, baked delicious cookies for the bake sale.

• Lastly, my mom baked delicious cookies for the bake sale.

Where should the comma be placed ?Yes while I was doing my homework I stumbled across some unknown words.

• after the word "yes"
• after the word "yes" and after the word "homework"
• after the word "homework"
• before the word "stumbled"

Where should a comma be placed? Well I guess I have to ride to bus home after all.

• after the word "
• after the word "well"
• before the word "after all"
• before the word "ride"