Which is a complex sentence?
A: Although I would rather visit Italy, I'm excited about going to Panama this summer.
B: Despite their large size, grizzly bears can run at speeds of up to thirty miles per hour.
The first sentence is the complex sentence. It is made up of an independent clause and a dependent clause. The dependent clause begins with the subordinating conjunction although.
Although I would rather visit Italy, I'm excited about going to Panama this summer.