3.6 Billion years ago cyanobacteria [sy-uh-noh-bak-TEER-ee-uh] caused the precipitation of calcium carbonate into structures of thin sheets of limestone. What is the name of these limestone sheets?

W) Stalactites [stuh-LAK-tyts]

X) Stalagmites [stuh-LAG-myts]

Y) Stromatolites [strou-MAT-l-uts]

Z) Trilobites [TRY-loh-byts]
Y) STROMATOLITES