If you know that a nation uses a parliamentary system of government, but have no other information, what do you know for certain about the structure of

a) who is allowed to participate in the governing process
b) the geographic distribution of power in the state
c) the relationship between the executive and legislative branches
d) that its laws must be collected in a written constitution

I believe the answer is: D) that its laws must be collected in a written constitution

In parliamentary system of government, the executive branch need the approval from the parliament in order to conduct a certain action.

Because of this, the system needs a written constitution to distinguish the power which limit the things that the executive branch can and cannot do.

C) the relationship between the executive and legislative branches.

Explanation:

A parliamentary system is one in which the executive power derives its democratic legitimacy from the trust it receives from the legislative branch. Moreover, the legislative branch is the one that holds the executive accountable. As this is a feature of all parliamentary systems, we can know for sure what the relationship between the executive and the legislative branches is. We cannot know for sure who is allowed to participate in the governing process or what the geographic distribution of power is. Finally, we also do not know whether its laws are collected in a written constitution (for example, the United Kingdom has a parliamentary system and an unwritten constitution).

c: in the east might be the correct answer