If a car was driving 45 miles per hour northeast, and is now driving 30 miles per hour north,
A
the car's velocity decelerated.
B
the car's velocity accelerated.
с
the car's velocity remained unchanged.
D
the car's acceleration is 30 miles per hour.

Lab reagent, hypothesis test.a reference solution used as a lab reagent is purported to have a concentration of 5 mg/dl. six samples are taken from this solution and the following concentrations are recorded: (5.32, 4.88, 5.10, 4.73, 5.15, 4.75) mg/dl.these six measurements are assumed to be an srs of all possible measurements from solution.they are also assumed to have a standard deviation of 0.2, a normal distributin, and a mean concentration equal to the true concentration of the solution.carry out a significance test to determine whether these six measurements provide reliable evidence that the true concentration of the solution is actually not 5 mg/dl.