The answer is C :
It controls the entry and exit of substances.
Answer:
<h3><em>to Separate camphor from sand we use <u>sublimation</u> process.</em></h3><h3 /><h3 /><h3><em>Hope </em><em>it</em><em> </em><em>is </em><em>helpful</em><em> to</em><em> you</em><em> </em></h3>
Because if you have a liquid then you need a glass to keep it together and when it is a solid it is already together so you don't need to do anything
Physical......................................................
