Some life forms move so slowly that their movement cannot be detected by normal observation. the best way to determine any movement is by placing a mark at some point, and observing any change in position from it. why is this true? a. the life form returns to that mark. bthe mark is a reference point. cthe mark is a standard unit. d. the mark makes measuring convenient.

B, the mark acts as a reference point.

Hello There!

Out of all these options i'd consider B to be the most suitable. As you can relate, it isn't very interesting watching a slow life form move along. You'd get bored .Instead, make a mark and then get back to it after a while and then you can see any changes from the point you left it. It makes it more convenient.

In short, option B is the best reason.

Hope This Helps You!
Good Luck :) 

- Hannah ❤