What is the smallest level of organization that can carry on all functions of life?

a. cells
b. organs
c. tissue
d. organ tissue

    Humans—and other complex multicellular organisms—have systems of organs that work together, carrying out processes that keep us alive.

   The body has levels of organization that build on each other. Cells make up tissues, tissues make up organs, and organs make up organ systems.

   The function of an organ system depends on the integrated activity of its organs. For instance, digestive system organs cooperate to process food.

   The survival of the organism depends on the integrated activity of all the organ systems, often coordinated by the endocrine and nervous systems.

b. the carbon cycle ensures living things have a source of hydrogen

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)]