Why are cyanobacteria important to early Earth? A. Cyanobacteria produced iron in Earth’s crust.

B. Cyanobacteria preceded the first photosynthetic organisms.

C. Cyanobacteria are the first photosynthetic organisms.

D. Cyanobacteria stopped the formation of rust in the Earth’s crust.

the correct answer, according to e2020, is the second choice there is an occluded front in region a and a cold front in region b.

the alkaline earth metals (beryllium (be), magnesium (mg), calcium (ca), strontium (sr), barium (ba), and radium (ra)) are a group of chemical elements in the s-block of the periodic table with very similar properties: shiny. silvery-white. hopefully this ? i didn't fully understand the question