What is the columbian exchange?

What are antigens and antibodies? how are they involved in the body’s response to incompatible blood?

Select all the correct answers. for a claim about the natural world to be considered scientific, what attributes must it have? a). it must be open to modification if new evidence doesn't completely support it. b). it must be based on scientific observations that can be repeated in a controlled setting. c). it must be applicable to future events and occurrences. d). it must be consistent with only a small portion of relevant observations or data.

Nitrogen-14 and nitrogen-15 are isotopes of the same element. how do these two isotopes differ? a. they have different numbers of nuclei. b. they have different numbers of protons. c. they have different numbers of neutrons. d. they have different numbers of electrons.