How can astronomers tell what a distant object's velocity is?
a by measuring the redshift or blueshift of the object
b by looking for particular lines in its spectrum
c by the frequency of the electromagnetic radiation it gives off
d by timing how long it takes light to reach the object and return

it is a

Why do bacteria thrive even in hostile environments

The nursing instructor has been observing nursing students initiate an iv infusion. which action(s), if made by the nursing student, indicates that further instruction is needed? (select all that apply.) the nursing student:

Many organizations release indexes used to measure the development of the world's countries. as we learned in this lesson, these indexes measure many factors, from life expectancy to happiness. in your opinion, what are the three most important factors we can use to determine how developed a country might be? explain your answers in a few sentences.