Plz help last question on my test 50.Which type of cell must be produced more frequently than the other types?

1)brain cells
2)red blood cells
3)muscle cells
4)liver cells
5)stomach lining cells

Which of the following statements is most likely correct about a rock belonging to the jurassic age and a rock belonging to the cambrian age? options: 1) they have identical fossils of organisms that have evolved over time. 2) both have animal fossils preserved in them due to weathering and erosion. 3) they contain different fossils because life on earth has changed through time. 4) the fossils in them were formed on the surface of earth due to exposure to sunlight.

Biology ! the conversion of inorganic carbon to organic carbon by plants during photosynthesis is known as _[blank]_. filtration immigration reabsorption primary production

Why are current extinctions of concern to enviromentalists?