Yahoo Answers is shutting down on May 4th, 2021 (Eastern Time) and beginning April 20th, 2021 (Eastern Time) the Yahoo Answers website will be in read-only mode. There will be no changes to other Yahoo properties or services, or your Yahoo account. You can find more information about the Yahoo Answers shutdown and how to download your data on this help page.

21 cm radiation comes from spin-flip transition that occurs in _____.?

a. very hot stars

b. globular clusters

c. open clusters

d. the so called "dark mass"

e. clouds of neutral hydrogen

3 Answers

Relevance
Still have questions? Get your answers by asking now.