Cells of the immune system are able to respond to the presence of invading organisms because they recognize the?

a. antigens on invaders
b. antibodies on pathogens
c. dna pattern in the nuclei of viruses
d. antibodies released from microbes

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)]

sodium i think the chemical element of atomic number 11, a soft silver-white reactive metal of the alkali metal group.

a researcher conducts an experiment on the secretion of a particular hormone in mice. scientists inject mice with a substance that stimulates the production of the hormone. the scientists then test the levels of hormones produced by the mice. the tool used to measure the hormones consistently detects the levels at 10 points lower than the actual hormone levels in the mice. this tool makes measurements, but the measurements aren't .

explanation:

no u