Consider the following planned experiment. which variable is being tested in this experiment? a. housing b. type of food c. vitamins d. amount of water

C. Vitamins

Explanation:

The factor Vitamin is being tested in this experiment. For an experiment to occur, it is necessary that we plan an experimental group as well as a placebo group (control group). In this experiment, all other factors have the same experimental group as well as the same placebo group except for the factor vitamin. The factor 'vitamin' has a experimental group in which the particular vitamin is given to the  object of test and a placebo group in which the vitamin is not given to the object of test. Hence, vitamin is the variable that is being tested in this experiment.

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)]