What are on the surface of most vertebrate cells, acting as markers of self?

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 applicable to future events and occurrences. b)it must be based on scientific observations that can be repeated in a controlled setting. c)it must be open to modification if new evidence doesn't completely support it. d)it must be consistent with only a small portion of relevant observations or data.