Astronomers can now report that active star formation was going on at a time when the universe was only 20% as old as it is today. When astronomers make such a statement, how can they know what was happening inside galaxies way back then?A. They look at open clusters in our galaxy and extrapolate to the past. B. They look at radio emission from quasars. C. They look at the way galaxy redshifts change with time. D. They examine the spectra of extremely high-redshift galaxies.

D.

They examine the spectra of extremely high-redshift galaxies.

Explanation:

Astronomers Measure Redshift and the most accurate way to measure redshift is by using spectroscopy. When a beam of white light strikes a triangular prism it is separated into its various components (ROYGBIV). This is known as a spectrum (plural: spectra).

With an estimated distance of about 32 billion light-years (comoving distance,) or 13.4 GLY (light-travel distance,) astronomers announced it as the mostdistant astronomical  galaxy known

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.

the best answer for these questions would be:

1.            c. is smaller

2.            d) concrete operational

3.            b) interaction with the environment – the children interact with their environment can them learn more.

4.            a) parents who reason openly with children can limit a child’s cognitive ability.