Ashark would not be a good index fossil because

a. salt water would degrade the fossil over time.
b. no fossil records exist for sharks.
c. it doesn't have structures that can be preserved in a fossil.
d. the species has survived for too long.

Ineed to get this test done which of the following statements is correct in hour our immune system responds to a potential pathogen? a.) the skin will be the first line of defense, and then the many phagocytes in the bloodstream will attempt to consume the possible pathogen. b.) b cells will start reading the antigen code immediately and call t cells to assist in destroying the pathogen. c.) the adapted immune system will call on the innate immune system to destroy the pathogen. d.) the t-cells in the adapted immune systems are the first to recognize the pathogen