To determine how long it will take Carla to read the full assignment, we first find out how long it takes her to read one page.
If it takes Carla 10 minutes to read 4 pages, then:
\[ \text{Time per page} = \frac{10 \text{ minutes}}{4 \text{ pages}} = 2.5 \text{ minutes per page} \]
Now, since Carla has 20 pages to read, we can calculate the total time it will take her to read all 20 pages:
\[ \text{Total time} = 20 \text{ pages} \times 2.5 \text{ minutes per page} = 50 \text{ minutes} \]
Therefore, it will take Carla 50 minutes to read the full assignment.
The correct answer is 50 minutes.