Problem: Roman Republic:

Over time, Roman architecture was modified as their urban requirements changed, and the civil engineering and building construction technology became developed and refined. The Roman concrete has remained a riddle, and even after more than 2,000 years some Roman structures still stand magnificently. The architectural style of the capital city was emulated by other urban centers under Roman control and influence. Roman cities were well planned, efficiently managed and neatly maintained.[citation needed]

What Roman construction material has continued to be a mystery to this day?
---
A: Roman concrete


Problem: Vacuum:

Fluids cannot generally be pulled, so a vacuum cannot be created by suction. Suction can spread and dilute a vacuum by letting a higher pressure push fluids into it, but the vacuum has to be created first before suction can occur. The easiest way to create an artificial vacuum is to expand the volume of a container. For example, the diaphragm muscle expands the chest cavity, which causes the volume of the lungs to increase. This expansion reduces the pressure and creates a partial vacuum, which is soon filled by air pushed in by atmospheric pressure.

What can a container spread and dilute?
---
A: unanswerable


Problem: States of Germany:

As the premiers did not come to an agreement on this question, the Parliamentary Council was supposed to address this issue. Its provisions are reflected in Article 29. There was a binding provision for a new delimitation of the federal territory: the Federal Territory must be revised ... (paragraph 1). Moreover, in territories or parts of territories whose affiliation with a Land had changed after 8 May 1945 without a referendum, people were allowed to petition for a revision of the current status within a year after the promulgation of the Basic Law (paragraph 2). If at least one tenth of those entitled to vote in Bundestag elections were in favour of a revision, the federal government had to include the proposal into its legislation. Then a referendum was required in each territory or part of a territory whose affiliation was to be changed (paragraph 3). The proposal should not take effect if within any of the affected territories a majority rejected the change. In this case, the bill had to be introduced again and after passing had to be confirmed by referendum in the Federal Republic as a whole (paragraph 4). The reorganization should be completed within three years after the Basic Law had come into force (paragraph 6).

Who addressed an issue if the premiers came to an agreement?
---
A: unanswerable


Problem: Late Middle Ages:

The term "Late Middle Ages" refers to one of the three periods of the Middle Ages, along with the Early Middle Ages and the High Middle Ages. Leonardo Bruni was the first historian to use tripartite periodization in his History of the Florentine People (1442). Flavio Biondo used a similar framework in Decades of History from the Deterioration of the Roman Empire (1439–1453). Tripartite periodization became standard after the German historian Christoph Cellarius published Universal History Divided into an Ancient, Medieval, and New Period (1683).

Along with the Late Middle Ages, what are the other three period of the Middle Ages?
---
A:
unanswerable