Which of the following requires the action of a first class lever in the body?
a. jumping
b. push-ups
c. waving
d. nodding

the activity that requires the action of a first class lever in the body is: D. nodding First class lever refer to a lever on which the resistance exist in one one side of the fulcrum and an effort is made on the other side. Another example of a first class lever beside nodding are: Scissors, a crowbar, or a seesaw

Smoking damages the respiratory system by inhalation of a foreign substance, that is absorbed and residue is left behind on our lungs sponge like substance. the gas that is inhaled also increase your blood pressure and dilates your blood vessels. also the process of inhaling and exhaling the smoke it causes irritation to the throat and mouth. smoking can cause lung cancer and other respiratory and circulatory diseases.