Answer: Fossils, Precambrian 
Explanation:)
 
        
                    
             
        
        
        
By Pleistocene ice age is meant the glacial periods that appeared in the Pleistocene. The Pleistocene is the first epoch of the Quaternary. It is an epoch when there was a so called ''ice age'' on the Earth, or rather a glacial period. During this ice age the planet had much lower temperatures on a global scale. The climate was also much drier. Lot of ocean water was frozen in the ice sheets that were stretching deep into the North American and Eurasian continents, which resulted in much lower sea levels that today as well. The places further north than 40 degrees of latitude were almost exclusively covered with ice, so life was almost impossible apart from some coastline places.
 
        
             
        
        
        
Percentage yield=(actual yield/theoretical yield) x 100%
 = (45/50) x 100%
 = 90%
        
             
        
        
        
Answer:
Yes.
Explanation:
"These starting substances of a chemical reaction are called the reactants, and the new substances that result are called the products."
There is a beginning product, and a reactant is needed in order for something to happen. 
For example, according to Newton, something cannot happen until an exterior force comes and stops/pushes it.
Sorry if this is incorrect, I am just 4th grade :(
 
        
             
        
        
        
I believe your answer is B.