A scientist measures the heart rates of 30 students from the same class before and after they run for different amounts of time. The experimental set up is
shown below:
• Group 1 had ten students who ran one lap.
• Group 2 had ten students who did not run at all.
• Group 3 had ten students who ran two laps.
Group 4 had 30 students from another class whose heart rates were
not measured.
Which group is the control in this experiment?
A. Group 1 from this class
B. Group 2 from this class
C. Group 3 from this class
D. Group 4 from another class

what are the statements

it’s previous models   because when i picked that son of a gun’s answer it was wrong look for previous models because they might make it a different letter  

as given the equation is

2al + 6 hcl > 2 alcl3 + 3 h2(g)

as per equation two moles of aluminum reacts with six moles of hcl to give two moles of alcl3 and three moles of hydrogen gas

given: three moles of al are present and 7 moles of hcl

for three moles of aluminum nine moles of hcl will be required

however as 7 moles of hcl are present so the limiting reagent is hcl

hcl is going to decide the number of moles of product formed

when six moles of hcl are present = 3 moles of h2 are formed

when one mole of hcl is present == 3/6 mole sof h2 will be formed

when 7 moles of hcl are present = 3 x 7/ 6 moles of h2 will be formed = 3.5 moles of h2