Based on the citation, ow does this clause represent a check on unlimited government power/

Section 7 of Article 1 of the United States Constitution grants power to the President of the United States to veto a bill passed by Congress. It also grants power to the Congress to override the President's veto.

Explanation:

By empowering Congress to override a veto of the President, the legislative branch of the Government has the power to prevent misuse of authority by the President thus providing a check on the powers of the executive branch of the Government. It also provides the President to veto the bill passed by Congress thus providing the executive branch to maintain a check on the powers of the Congress.

first, the romans stayed isolated because they had to defend their own territories from neighboring cities that were harassing them, like the etruscans. second, once the romans managed to defeat their neighbors, and started to expand their territory, they started to build roads and bridges. finally, now that the romans have covered their territory with roads functioning as highways, they could mobilize their legions faster to assemble larger military units in a specific place.