Combine simple sentences to make compound/complex
The cat wears many costumes. He hates it. (Although)
Although the cat hates it, he wears many costumes.
The giraffe is munching on some leaves. He's hungry. (Since)
Since the giraffe is hungry, he is munching on some leaves.
The puppies will be happy. They get a treat. (If)
If the puppies get a treat, they will be happy.