Which of the following type of immunity is present at the time of birth and is a non-specific type of defence in the human body?

The correct answer is Innate Immunity.

Let us break down the concepts of immunity to understand why this is the correct choice:
1. Innate Immunity: This is the defense system with which a person is born. It is a non-specific type of defense, meaning it does not target a specific pathogen but provides a general barrier and immediate response against any foreign invaders (like physical barriers such as skin, and chemical barriers like stomach acid).
2. Acquired Immunity: Also known as adaptive immunity, this type of immunity is not present at birth. It is pathogen-specific and is acquired during an individual's lifetime after exposure to specific foreign agents or pathogens.
3. Cell-mediated Immunity: This is a component of acquired immunity mediated by T-lymphocytes (T-cells) that destroys infected cells directly.
4. Humoral Immunity: Also a component of acquired immunity, this is mediated by antibodies produced by B-lymphocytes (B-cells) circulating in the body fluids (humors).

Since the question asks for the immunity present at the time of birth and characterized by a non-specific defense mechanism, the correct option is Innate Immunity.