It's closeness im pretty sure
Answer: Well if you look at the questions all of these are plans so im not exactly sure but the most valid answer ould be ( B )
Astronauts in the future are planning to expllre mars because they think that it is possiable for humans to live on the planet mars.
Hope this helps in some way have a great rest of your day :)
I assume you meant which method is least reliable for identification.
If so, the answer would be COLOR, since there are many minerals that are different, yet share similar color. So it wouldn't be reliable to identify a mineral based off it's color.
