Why brain was protected with hard skull

In which of the following ways is the function of the surface of a microsphere similar to the function of an actual cell membrane? a. both make it possible for the conditions in the interior to be different from the conditions outside. b. both provide a barrier that keeps water from flowing across it so the interior remains dry. c. both separate the rna that forms in the interior from any rna that might form in the environment. d. both can actively move molecules into the interior or out into the surrounding environment.

Which property is used to identify the origin of an igneous rock? color density hardness crystal size

If you have a difficult time knowing where your hand is without looking at it you may be having a problem with your what ?