Answer:
B. Color perception is achieved by activation of various combinations between the tree cone types.
Explanation:
Human eye have only three photo receptor ( three wavelength) but they can see several thousands of shades of color because color perception is gained by combination of these three wave length cone types ( RED, BLUE AND GREEN) into various combinations. Our retina have two types of cell:- cone cells and cylindrical cells. Cone cells are responsible for the identification of color.
A molecule, would be the correct answer
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A. a steel beam. All of the rest of them change shape or volume whereas a steel beam with never change in volume or shape.
(b) 71%
The thermal efficiency of a Carnot heat engine is given by:

where
W is the useful work done by the engine
is the heat in input to the machine
In this problem, we have:
is the heat absorbed
is the work done (175 kJ is the heat released to the sink, therefore the work done is equal to the difference between the heat in input and the heat released)
So, the efficiency is

(a) 
The efficiency of an engine can also be rewritten as

where
is the absolute temperature of the cold sink
is the temperature of the source
In this problem, the temperature of the sink is

So we can re-arrange the equation to find the temperature of the source:
