In the human respiratory system, what structure prevents food from entering the trachea during swallowing?

Which law of thermodynamics states that absolute zero cannot be reached in a finite number of steps?

What type of lens converges light rays to a single point?

What is the function of the respiratory system?

Which of the following is an example of a non-contact force?

Which structure connects the two halves of a neuron, allowing communication between them?

What is the product of the combustion of hydrocarbons in the presence of oxygen?

Which of the following is an example of a polymer?

Which of the following is an example of a homogeneous mixture?

What is the main function of the immune system in the human body?