Final answer:
A lack of strong structural wood significantly limited the construction choices of the early Sumerians in Iraq, driving them to utilize sun-baked bricks and clay as primary building materials for their sophisticated architectural achievements.
Step-by-step explanation:
The factor that limited the choices of construction systems available to the early people of Sumeria in Iraq was a. Lack of strong structural wood. Due to the natural resources accessible in Mesopotamia, building materials such as strong timber were scarce. Instead, the civilization made extensive use of materials that were readily available, like sun-baked bricks and clay, which shaped their architectural designs and construction methods markedly.
With an environment deficient in wood, large stones, and precious metals, the early Mesopotamian people adapted by utilizing the abundant clay to create mud bricks, which became the primary construction material. Their technological advances in areas like irrigation and manufacturing of bronze were also crucial in supporting the growth of cities and the standing of Sumer as a significant cultural and technological hub. Furthermore, their ingenuity in architecture was demonstrated by developments such as the early use of the round arch seen in the famed Ishtar Gate.
Despite the resource constraints, the early Sumerians achieved a remarkable level of skill in construction and artistic production, as evidenced by their monumental architecture and intricate craftsmanship in other areas such as the decorative arts. The success of Sumerian construction was owed to effective state management of agriculture and trade which generated the surplus necessary to support their society's architectural endeavors.