Which of the following is true regarding extinction?
a. extinction that occurs in a relatively short period of time is referred to as background extinction.
b. single events or several causes working together to produce extinction in a short period is referred to as mass extinction.
c. if the rate of speciation in a clade is equal to or less than the rate of extinction, the clade will survive.
d. the rate of extinction is steady from clade to clade as are the number of species contained within a clade.

sand 60

clay 10

silt 30

sandy loam should be dominated by the sand. as the amount of sand increased, the amount of slit needed to anchor the plants' roots to the sand will also be increased. even though the amount is very little, 10% part of clay is still necessary for proper oxidation.

some fungi obtain their nutrients from a living host (plant or animal) and are called most biotrophic fungi have fairly narrow host ranges—they are specialized on a limited called rhizomorphs that allow the fungus to grow from one tree to another. ascospores are formed inside a sac-like structure called an ascus. so your answer is a