What is the main function of the human immune system? O A. To protect internal organs and assists in movement
O B. To collect and respond to information about the internal and
external environment
O C. To protect the body against infection
D. To transport oxygen and nutrients to the body's tissues

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.

trachea, alveoli, lung capillaries, arteries

answer: zinc is the substance which has a volume of 1.38 .

density is defined as the mass of an object per unit volume.

it can be calculated by dividing mass of a substance by its volume i.e.

si unit of density is kg per cubic meter and cgs unit of the same is gram per cubic centimeter.

now from the given data volume can be calculated by the formula .

hence, the volume of aluminium will be = which comes out to be 1.703 .

similarly, volume of zinc, chromium, and nickel will be 1.378 , 0.869 , and 0.356 respectively.

the circled areas are referred to   as sunspots.   the sunspots are cooler than the   surrounding area.

sunspots are temporary phenomena on the photosphere of the sun that appear visibly as dark spots compared to surrounding regions. they correspond to concentrations of magnetic field flux that inhibit convection and result in reduced surface temperature compared to the surrounding photosphere.