On the geologic time scale are marked by major, striking, and worldwide changes in the type of fossils present.
a.
eras
c.
epochs
b.
periods
d.
all of the above

Long term exposure to waves can cause sunburns and skin cancer.

When a human or animal consumes food, the carbon in that food is most likely to be converted into which of the following elements? a. carbon remains carbon b. nitrogen c. oxygen d. hydrogen

Guard cells control which event? the growth of plants capture of solar energy gas exchange in leaves water absorption in roots