Which of the following is a problem faced by the global economy?

answer : haversian

[explanation: -(compact bone is organized as parallel columns, known as haversian systems, which run lengthwise down the axis of long bones. these columns are composed of lamellae, concentric rings of bone, surrounding a central channel, or haversian canal, that contains the nerves, blood vessels, and lymphatic system of the bone)]

oxygen = 21% of the atmosphere

nitrogen = 78%

carbon dioxide = 0.1%

argon =0.934%

where in your body is there an enzyme that does function at a high or low ph? what is the name of that enzyme and its function?

this is more of a statement than a question. is there answers to go along with this, or is it opinion based?