The correct answer to this open question is the following.
Although there are no options attached, we can say the following.
What is a one-house legislature?
A one-house legislature is a form of legislature in the structure of government that only has one chamber in Congress, instead of two.
This legislative or parliamentary system is common in today's' democratic nations. Some nations that have this unicameral system are Denmark, Bulgaria, Turkey, Ukraine, Sweden, and Hungary.
The United States has a bicameral system in Congress, where the upper chamber is the Senate and the lower chamber is the House of Representatives. This bicameral system helps to balance power and interests between legislators.