Assertion  :       Histamine is involved in allergic and inflammatory reactions.

Reason     :       Histamine is a vasodilator

1. If both the assertion and the reason are true and the reason is a correct explanation of the assertion
2. If both the assertion and reason are true but the reason is not a correct explanation of the assertion
3. If the assertion is true but the reason is false
4. If both the assertion and reason are false

Assertion   :       Heart valves resemble swing doors in action.

Reason      :       Valves are present in the heart chamber, at the opening of the heart into large arteries and veins.

Assertion     :  Closed circulatory system is more effective than open type.

Reason        :  The closed circulatory system considerably enhances the speed, precision and efficiency of circulation.

Assertion   :       Cardiac output rises during exercise.

Reason      :       Cardiac output helps in less oxygen consumption.

Assertion    :       EEG is of immense diagnostic value in the cardiac diseases.

Reason      :       Defects in cardiac functions can be reflected in changes in the pattern of electrical potentials recorded in the EEG. 

Assertion   :       An artificial pacemaker can replace the sinoatrial node of heart.

Reason      :       This is because, an artificial pacemaker is capable of stimulating the heart electrically to maintain its beats.

Assertion   :       Mixing of oxygenated and deoxygenated blood occurs in reptilian and amphibian hearts.

Reason      :       This happens because of the incomplete partitioning of the auricle.

Assertion   :       Left ventricle of heart has a thinner wall than that of the right ventricle.

Reason      :       Left ventricle needs to pump blood to nearby lungs only.

Assertion   :       Heart of fish contains only deoxygenated blood.

Reason      :       Oxygenated blood do not return back to the heart in fishes.

Assertion   :       Blood flows at a very slow velocity in the lacunae and sinuses of prawn.

Reason      :       This happens because of the absence of heart in the prawn.