Chata suffered a rather severe injury to her brain as the result of a bike accident. Now she can no longer remember things that happened before her injury. Chata would be BEST described as suffering from:

Chata would be BEST described as suffering from Retrograde Amnesia. Retrograde Amnesia is a type of memory loss which happens after an injury, also retrograde amnesia can be either temporary, permanent, or ends up getting worse over time. Something interesting about Retrograde Amnesia, is that you may lose your memories, but if you have a skill like drawing or playing the piano, you will still remember how to do those.

your answer is rna to the question.

the answer is; comparing the frequency of collisions with and without the device

this makes the anti-collision system an independent variable and the collisions a dependent variable. if there are fewer collisions with an anti-collision system that without, then it can be stated that the system is a success. essentially, collisions under an anti-collision system are compared with the frequency of collisions by cars with the human drivers.