How is PCI Express different than PCI?

The PCI Express bus architecture sounds similar to the PCI bus architecture. What is the primary architectural difference between PCI and PCI Express?

A) PCI provides for higher throughput than PCI Express

B) PCI is a parallel bus architecture and PCI Express is a serial bus architecture

C) PCI has more communication lanes than PCI Express

D) PCI is a newer specification than PCI Express

E) PCI Express has way more letters than PCI