Which of these describes how heat transferred by convection?
a. warm air rises and takes heat with it; eventually it cools and sinks
b. air molecules touch the warm ground, heating it up
c. land and ocean absorb and re-emit heat from the sun
d. sunlight travels through space without the aid of fluids or solids

Which of the following particles always has a positive charge? a. electronb. neutron c. proton d. ion

Which of the following statements is true about the relationship between genetic variation and natural selection? a. genetic variation must be present in a population before natural selection can act on it. b. genetic variation arises in a population as a result of natural selection. c. natural selection can act on a population whether there is genetic variation within the population or not. d. after natural selection acts on a population, the amount of genetic variation in the population always increases.

What contributes to the high level of biodiversity found in wetlands? a. the large amount of available organic matter to organisms that are food for larger organisms b. the amount of available water for organism use c. the high nutrient availability d. all of the above select the best answer from the choices provided a b c d