Stream tables are used for modelling erosion
1 a. The features of the model that will help Armando answer the question 
are; The adjustable legs of the stream table, sand and water source.
1 b. To test the idea that very steep hills lead to narrow deep rivers, can 
adjust the table legs using a specific sand size and record the results.
1 c. To test the idea that very small sand grains lead to narrow, deep rivers 
Armando can try sands of different sizes, with the table legs fixed at a given 
location and record the result.
2. The result from the model that would be evidence that Armando's idea is 
correct is increase in water path depth with steepness of the stream table.
Reasons:
A river flows due to gravitational forces pulling water from a higher section 
to a lower elevation. The speed of flow depends therefore, on the 
steepness of the slope over which the river flows.
The energy of the flowing water removes items from the ground such as 
sand, granite, and mud as well as water soluble materials such as 
limestone as it flows.
Depending on the speed with which the river flows, the river has more 
force to remove more materials, and the river flows faster when narrow 
than wide, therefore, being able to remove more material, which develops 
into a deep and narrow river.
Therefore;
The river is narrow and deep because of the steep hill and the presence of 
small sand grains in its path.
1 a. The features in the model that will help Armando answer the question are;
- Elevated water tank (water source)
- The adjustable table legs
- Hole for water exit at the lower end of the stream table
 1 b. To test the idea that very steep hills lead to narrow, deep rivers, the 
depth of the path of water through the sand is measured each time the 
adjustable legs are adjusted closer to the lower end of the stream table 
increasing the steepness of the table and recording the findings;
[tex]\begin{array}{|c|c|c|}Leg \ position & Width \ of \ water \ path &Depth \ \ of \ water \ path \\1&&\\2&&\\3&&\end{array}[/tex]
1 c. Armando can test the idea that very small sand grains lead to narrow, 
deep rivers by keeping the leg position fixed and measuring the depth and 
width of the water path formed using grades of sand of different sizes.
[tex]\begin{array}{|c|c|c|}Sand \ grade & Width \ of \ water \ path &Depth \ \ of \ water \ path \\1&&\\2&&\\3&&\end{array}[/tex]
2 The result from the experiment that would be evidence that Armando's 
idea is correct is the result from the tests involving the changing of the 
adjustable leg positioning that increasing the steepness of the slope 
increases the depth and narrowness of the water path through the sand.
Learn more about stream tables here:
https://brainly.com/question/21549297