Why is competition for biotic resources a key factor in the success of an organisms or a population in an ecosystem

i think a) betsy can donate only blood to mark is correct because, mark and betsy have the same blood type. whereas nobody else has b+ blood so betsy can't donate to them.

i'm thinking (a) to keep sand in place; ////////////

explanation: a sand fence or sandbreak, like a snow fence, is used to force windblown, drifting sand to accumulate in a desired place. sand fences are employed to control erosion, sand dune stabilization, keep sand off roadways, and to recruit new material in desert areas.

that scientist would be robert hooke

your body is trying to warm itself up. or more precisely, sensors in your skin send messages to your brain to generate heat to your body.