The best and most correct answer among the choices provided by your question is the second choice or letter B.
The researchers’ conclusion was not justified because t<span>he control group was not treated the same as the experimental group.</span>
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Answer:

Explanation:
To solve the problem, the concepts related to the magnetic field and the current produced in a lightning bolt are necessary.
The current is defined by the load due to time, that is to say

Where,


So the current can be expressed as:


Once the current is found it is now possible to find the magnetic field, as this is given by the equation,

Where,
Permeability Constant
I= Current
r= radius
Replacing the values we have


The velocity of the girl is -4.8 m/s.
Using the principle of conservation of linear momentum, The total momentum of bodies before and after collision is constant. Since the two objects are stationary, the initial momentum of each body is zero.
Thus;
0 = (80 × 3) + (50 × v)
0 = 240 + 50 v
-240 = 50 v
v = -240/50
v = -4.8 m/s
Note that the negative sign shows that the velocity of the girl is in opposite direction that that of the girl.
Learn more about momentum: brainly.com/question/904448
Answer:
c. find the slope of the velocity time graph
Answer:
The temperature of cold reservoir should be 246.818 K for efficiency of 35%
Explanation:
In first case we have given efficiency of Carnot engine = 26 % = 0.26
Temperature of cold reservoir 
We know that efficiency of Carnot engine is given by



For second Carnot engine efficiency is given as 35% = 0.35
And temperature of hot reservoir is same so 
So 

So the temperature of cold reservoir should be 246.818 K for efficiency of 35%