Which of the following is a testable hypothesis?

What sre the effects of hemolytic disease of a newborn

The relationship between intron and exon

Which of the following must be true for a fossil organism to be useful as an index fossil? a. the fossil organism must be widespread geographically. b. the fossil organism must be abundant. c. the fossil organism must be limited to a short span of geologic time. d. all of the above.