Pleura membranes secrete mucus to reduce friction during breathing. What causes the friction during breathing?

the most common type of reef is the fringing reef. this type of reef grows seaward directly from the shore. they form borders along the shoreline and surrounding islands.

d.embryo is the correct one

answercells,tissues,organs,organ,system-organism;

levels of biological organization; organism,population,community,ecosystem,biome,biosphere,

hope this .good luck