Commas vs Semicolons

There are negative side effects to smoking_ _here are no positive effects.

If you pick the comma_ it proves that my grammar activities are fun. Haha suckers.

You know who is a really amazing_ awesome person? Read the first word. 

When you asked for a pet elephant_ he gave you a whale.

"I have seniority so this is fine."_ I tell myself as I plow through the underclassman.

I demanded pizza today_ but Chipotle will suffice.

The sun is a great place_ therefore_ I plan to go there on my birthday

The little boy enjoys white vans_ he dislikes black vans.