English: Cardiovascular efficiency depends on a number of factors. One measure is called stroke volume, which is the volume of blood pumped per heartbeat. A fit individual has a larger stroke volume, which means a greater volume of oxygen is delivered to the body per heartbeat.
Spanish: La eficacia cardiovascular depende de una serie de factores. Una medida se denomina volumen sistólico, que es el volumen de sangre bombeada por latidos cardíacos. Un individuo en forma tiene un volumen de movimiento mayor, lo que significa que un mayor volumen de oxígeno es entregado al cuerpo por latidos cardíacos.
        
             
        
        
        
The answer to the question '<span>In a series of undisturbed rock layers where shale lies between sandstone below and limestone above, the __." would be limestone is youngest. Out of all the rock layers, the limestone is dated to be the youngest of all.</span>
        
                    
             
        
        
        
"The total distance traveled divided by the time it takes to travel the distance"
That's actually a pretty good definition of average speed. <em>(A)</em>
 
        
             
        
        
        
Answer:
C. Fill two identical pots with equal volumes of salt water and tap water and use a stopwatch to determine the time it takes each pot to boil.
Explanation: 
<u>A) is incorrect</u> because Peter should have the same testing environment for both of his experiments. 
He should choose the same method of boiling the salt water and tap water because the stovetop and the microwave could also affect the results and make them unreliable.
<u>B) is incorrect</u> because Peter should not estimate the time it takes the salt water and tap water to boil. 
Peter should measure and record the amount of time that it takes these substances to boil in order to have an accurate, valid experimental thesis.
<u>C) is correct</u> because Peter uses the same volume of salt water and tap water, fills them into two identical pots, and uses a stopwatch to determine the amount of time it takes each pot to boil.
The stopwatch makes the experiment more valid and accurate compared to the previous methods, and the identical pots and amounts of water help this experiment become even more precise.
<u>D) is incorrect</u> because the variables in the experiment are not controlled amounts and will therefore produce an inaccurate and invalid experiment. 
 
        
                    
             
        
        
        
They are dynamic, with winds and waves constantly reworking and moving
the barrier island sand. 
Changes in sea level also affect these islands.
Most scientists agree that sea level has been gradually rising over the
last thousand years, and this rise could be accelerating today due to global warming. 
Rising sea level causes existing islands to migrate shoreward.