All of the following are reasons why astronomers have difficulty looking at distant stars except: a. some stars are so far away, even the best telescopes are not powerful enough. b. they don't understand how redshift affects stars. c. there is a lot of gas and dust in the atmosphere that distorts the light coming from stars. d. there is a lot of light pollution on earth.

Option B: They don't understand how redshifts affects stars.

There are millions and billions of stars in our universe. Scientists study stars using telescopes. But some stars are so far, that even the best powerful telescopes are not able to detect their light. Also, the interstellar distance is filled with clouds of dust and gas which makes some part of the universe opaque. It becomes difficult to study stars using earth based telescopes due to lot of light pollution. Astronomers understand how redshifts affects stars and hence, are able use this to study stars via their spectrum. Hence, astronomers don't understand how redshifts affects stars is a wrong reason of why they face difficulty in looking at distant stars.

b.a device that inputs heat into a cool object