Which resources was said to have cities named for it and was a large part of the reason Europeans explored and eventually settled in what is now Texas?

A: silver
B: Iron
C: diamonds
D: Gold

The correct answer is D: Gold.

To find the answer, let's break down the question and analyze the options. The question states that a specific resource was said to have cities named for it, which influenced Europeans to explore and settle in what is now Texas.

Option A: Silver - While silver was a valuable resource during European exploration and settlement, it was not directly linked to cities being named for it in Texas.

Option B: Iron - Iron, though an important resource, was not the main reason for European exploration and settlement in Texas. Additionally, there are no cities specifically named after iron in Texas.

Option C: Diamonds - Diamonds were not a significant resource that motivated Europeans to explore and settle in Texas. Moreover, there are no cities named after diamonds in the state.

Option D: Gold - Gold was indeed a valuable resource that played a significant role in attracting Europeans to explore and settle in Texas. This is further supported by the fact that there are several cities in Texas named after gold, such as Goldthwaite and Goldsmith.

In conclusion, the correct answer is D: Gold. The availability of gold was a major motivation for European exploration and settlement in what is now Texas, and this is evident in the presence of cities named after gold in the region.