Complex organisms with gills and lungs were major life forms that existed in

a.

mesozoic era

c.

precambrian era

b.

cenozoic era

d.

paleozoic era

D-Paleozoic era.

Complex organisms with gills and lungs were major life forms that existed in the Paleozoic era.

The earliest and the longest of the the Phanerozoic era is the Paleozoic era. The Paleozoic era is divided into 6 geologic periods namely the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian.

the correct ansewr is D)  paleozoic era

the real answer is b. scintillation counter