What makes astronomers think there are black holes in space?
1.when galaxies dissapear, they stop emitting infrared radiation, and a hole in space is formed
2.there are areas of space from which no electromagnetic energy of any kind has been deleted
3.at the end of a star's life cycle, it runs out of hydrogen and stops emitting visible light
4.bursts of light that release large amounts of radio waves precede the formation of a black hole

Drag each label to the correct location on the image. each label can be used more than once. a scientist introduced mutations in a gene sequence isolated from bacteria. study the sequence, and identify the steps where the mutations may affect the formation of proteins. in the sequence, black letters stand for protein coding regions and red letters stand for noncoding regions. protein will not be changed. protein may be changed. attcgtgttc atcgtgttc atcgtattc attcgtattc

Chalk is an ionic compound. which is a property of all ionic compounds that makes chalkboard? particularly useful for writing on a a high melting point hardness and brittleness inability to dissolve in water a multicolored appearance

How many species of living things are alive on earth today? more than 1,000,000 none of these answers are correct 100-500 1,000 –500,000 o 500,000 -1,000,000