What is the contribution made to the development of the microscope by charles   spencer?   a. first to document careful observations of different cell types  b.identifying the first cell c. used mathematics to improve the focus of the lens  d. created the  first microscope e. discovered the electron microscope  f. built microscopes capable of magnification of up to 1250 x using regular light

built microscopes capable of magnification of up to 1250 x using regular light

The law of superposition asserts or states that the rocks that a deeper or lower in the Earth are older than the rocks that are above them.
 
For example, let's say you have 3 different layer of rocks (Layer A, layer B, and layer C). Let's say layer A is on top of layer B and layer B is on top of layer C. So, how do you know which is older? Based on the law of superposition, Layer C would be the oldest of them all and layer A would be the youngest or relatively new layer. 

For definite age of these rocks, you would need to use some radiometric dating. 

Hope that helps!