A phosphate, a sugar, and a nitrogenous base form a...?

Which of the following statements is true? 1. the mantle of the earth is made of solid nickel and iron. 2. the crust of the earth is made of solid nickel and iron. 3. the inner core is made of solid nickel and iron.

Natural selection changes allele frequencies because some survive and reproduce more successfully than others.

Based on the data in the graphs do you think pepsin and trypsin are found in the same part of the body? explain your answer.