The seasons on earth, change as the Earth tilted on its axis, and revolve in a loop around the Sun every year. Summer takes place when the hemisphere tilted to the Sun, whereas winter takes place tilted away from the Sun. This tilting is the primary reason for the 4 seasons of the year - summer, autumn winter and spring.
The tricuspid valve shuts. This prevents blood from flowing backward into the right atrium while the ventricle contracts. So, your answer will be the Tricuslid Valve. Hope I helped!
