Answer: Potassium-40 decays into argon gas over time.
Explanation: Potassium-argon dating is a dating method used to determine the age of sedimentary rocks by comparing the proportion of K-40 to Ar-40 in a sample of rock, and knowing the decay rate of K-40.
Potassium-40 undergoes decay following first order kinetics as given below:

The answer bnb is true becuase without desity in anything nothing would circulate
Answer:
Water, carbon dioxide, and oxygen are among the few simple molecules that can cross the cell membrane by diffusion (or a type of diffusion known as osmosis ). Diffusion is one principle method of movement of substances within cells, as well as the method for essential small molecules to cross the cell membrane.
Answer:
Okay. Adelie penguin, Crabeater (?) seal and emperor penguin = krill
Leopard Seal, Weddell seal = fish
Toothed whales will eat a lot of stuff, it's a genus, but a common food is = squid
Baleen (?) whale = phytoplankton, other zooplankton
Parasite or host... Whales have barnacles but that's is the only "host" on this list. I listed food by matching the predators to prey in the list, sorry if it doesn't help, maybe be more clear?
I need more context to answer. What are the statements?