Answer: Organizational culture
Explanation: Organizational refers to the group of factors that affects social and psychological environment within the organisation. These constituents reflects the values and beliefs of the organisation.
In the given case, the employees in the company are under the age of 40. This illustrates that the company beliefs in employing young blood. The informal communication shows the open culture of the organisation depicting freedom to the employees.
Hence from the above we can conclude that the correct option is D.