Which statements describe dark matter? Select two options.

A:It is invisible.
B:It is the same as dark energy.
C:It is well understood by scientists.
D:It does not emit electromagnetic radiation.
E:It can be observed by shifts in red and blue light

The picture below shows two galaxies. spiral galaxy and elliptical galaxy which of these statements best describes a similarity between the two galaxies? (2 points) both have elongated centers. both have centers shaped like bars. both change their shape from time to time. both are held together by gravitational forces.