Which feature signifies to astronomers that a distant star is part of a planetary system? a.) the star periodically dims. b.)the star expands into a red giant. c.)the star moves through the sky. d.)the star continuously gets brighter.

a) The star periodically dims.

A star is the body of gas in which nuclear fusion of gases like helium and hydrogen  takes place due to this reason the star glows or dim. Star gets the ability to generate light because of this nuclear fusion which  cannot be observed in planets although the process of generation of star and planet is the same.  In distantly located star under observation, it's luminosity ( the property of  emitting lighting) is controlled by size of the star, the larger the size of the star it will have greater surface area the more profound will be the nuclear fusion in it and more light will be emitted. Second factor is the gaseous interaction of gases in and around the star and their temperature which causes the change in the light which has to pass through a layer of these gases. Therefore,  the distant star observed will show light fluctuations.

q: compare the parts of a cell and the cell as a whole to another common nonliving system (i.e., a car, a city,

a:

comparing this to the inside of a food building/company.

all cells are surrounded by a plasma membrane, which protects the cell from its environment, keeping toxic substances out of the cell. it regulates which molecules are allowed to enter and exit the cell.

regulates all cell activity such as cellular metabolism, and growth in addition to storing and maintaining the cell's dna for transcription and replication. determines what proteins to make.

contains the organelles; site of most cell activity

the place where ribosomes do their working activity.

builds the proteins.

prepares proteins for use or export.

responsible for breaking down and absorbing materials taken in by the cell.

maintains cell shape.

transforms one form of energy into another.

phylogenetic tree is the tree of life or evolution tree. it shows the different branches of evolution. the sequence goes like tissues - coelom - backbone - endoskeleton - segmentation