All of the following are common types of pain stimuli except a. visual b. mechanical c. chemical d. thermal

Answer: Option A visual

Explanation:

1. Mechanical - A mechanical stimulus is perceived by actions such as stretching or application of high pressure.

2. Thermal - A thermal pain stimulus is generated due to temperature changes such as extreme heat or cold.

3. Chemical - A chemical pain stimulus is generated by chemicals such as acids which are applied eternally or by chemicals produced inside the body such as serotonins, bradykinin etc.

As, the pain stimuli are only of three types - mechanical, chemical and thermal, we can conclude that there is no visual stimuli for pain.

b. heterotroph

explanation:

trachea, alveoli, lung capillaries, arteries