The diagram illustrates the valves inside the heart. When the atria are relaxed and the ventricles are contracted, which valves are open and which are closed?
- Aopen: 3 and 4; closed: 1 and 2
- Bopen: 2 and 4; closed: 1 and 3
- Copen: 2 and 3; closed: 1 and 4
- Dopen: 1 and 4; closed: 2 and 3