Pretend you are a teacher preparing a quiz for the text I will provide. 
            Each quiz question should follow the format below. 
            Ensure that you carefully recheck the questions and answers for accuracy. 
            The output should be a ready-to-use list of dictionaries for the Python eval function:

            [

                    "question": "WRITE THE QUESTION HERE",
                    "options": ["A) OPTION_1", "B) OPTION_2", "C) OPTION_3", "D) OPTION_4"],
                    "answer": INDEX_OF_CORRECT_ANSWER_IN_OPTIONS_LIST,
                    "explanation": "EXPLAIN WHY THE ANSWER IS CORRECT"

            ]

            Text:
            . 
There are two types of X-ray generated: characteristic radiation and bremsstrahlung radiation. 
Direct and indirect action of radiation:
In direct action: the free electrons resulting from ionization interact with DNA molecule directly
In in- direct action: the free electrons resulting from ionization interact with water molecules inside the body and creates "free radicals". 

fluid mechanics
Fluid Mechanics (part 1: fluid static)
Density:
Definition: mass Density is the mass m of substances divided by its volume v.
ρ= m/v       [SI unit of mass density Kg/m3 ]
Example 1: (blood as a fraction of body weight)
 The body of man whose weight is 690N contain about 5.2 x 10-3 m3 of blood, (a) find the bloods weight. (b) express it as a percentage of a body weight.
Solution: (density of blood = 1060 Kg/m3) 
Bloods weight   W=mg= (ρv). g= (1060 x 5.2 x 10-3)x 9.8= 54 N
Percentage of bloods weight to the body weight   Percentage% = (54/690)x100= 7.8% 


Pressure:
Definition: Pressure is the force exerted on a surface per unit area.
P=F/A    SI unit is Pascal (1 Pa= 1 N/m2)     , [ in CGS : unit will be dyne/cm2]
Other units:  1atm= 1.013 x105 Pa= 760 mm Hg
                            1 torr = 1 mm Hg.
Example 2: estimate the force exerted on your eardrum due to the atmospheric pressure if the area of the eardrum is 10-4 m2.
Solution:
The atmospheric pressure P= 1 atm= 1.013x105 N/m2 (Pa)
The area = 10-4 m2
P=F/A                F=PXA= (1.013x105) X (10-4) = 10.13 N.



Manometer:
Used to : measure the pressure of a gas contained in a vessel is the open tube manometer.  
The gas presure P=P0 + ρgh [P is  absolute pressure].
So, the difference in pressure P- P0 = ρgh
P- P0  called  "gauge pressure" 



Surface Tension
A small insect resting on the surface of a pond or lake is a common sight in the summertime. If you look carefully, you can see that the insect creates tiny dimples in the water′s surface, almost as if it were supported by a thin sheet of rubber. In fact the surface of water and other fluids behaves in many respects as if it were an elastic membrane. This effect is known as surface tension. In fact, even a needle or a razor blade can be supported on the surface of water if they are put into place gently, even though they have densities significantly greater than the density of water. 

SURFACE TENSION
Definition (1): The work done per unit area  in increasing the surface area of a liquid.
T= work done(joule or erg)/increase in  surface area (m2 or cm2) [Unit: J/ m2 or erg/  cm2 ]

Definition (2): The force acting  perpendicular per unit length.
T= force (newton or dyne)/increase in length  (m or cm) [Unit: N/ m or dyne/ cm ]
THE SURFACE OF LIQUID
Cohesive force
between	like	molecules
It	is	the	interaction	forces
,	i.e.
liquid molecules.
Adhesive force
It is the interaction forces  between unlike molecules, i.e.  liquid molecules and glass  container molecules.
ADHESIVE FORCE > COHESIVE FORCE THE SURFACE IS CONCAVE
ADHESIVE FORCE < COHES

            Quiz: