Cells lining the trachea have whiplike motile extensions on their free surfaces. what are these extensions, what is their source, and what is their function?

Which statements explains what the fossil records indicates? check all that apply. a) earth is 4.5 billion years old b) many organisms have become extinct c) mammals have always existed on earth d) mass extinctions have occurred several times on earth e) the amount of water on earth has decreased over time?