Complex sentence: Moments later, Dr. Roberts appears, rejoicing after an unexpected trip to Woodstock, and proudly gives Michael an "A" grade on his science project under the condition that he gets rid of the machine because it's something mankind is not ready for.
Split into simpler sentences: Moments later, Dr. Roberts appears, rejoicing after an unexpected trip to Woodstock, and proudly gives Michael an "A" grade on his science project. He tells him to get rid of the machine because it's something mankind is not ready for.