Answer:
A & C
Step-by-step explanation:
Four conditions are needed for natural selection to occur: reproduction, heredity, variation in fitness or organisms, variation in individual characters among members of the population. If they are met, natural selection automatically results.
YES - A) You must have variation in the population, typically in the terms of "fitness" or having admirable/sucessful traits that make them more likely to reproduce and ensure their own offspring are fit too.
NO - B) It is sexual (not asexual) reproduction that uses natural selection for their offspring. Although some asexual organisms use natural selection, it is ALWAYS used if possible with natural selection to ensure the fitness of characteristics is passed down.
YES - C) Competition is necessary for natural selection to occur. When those who are more physically fit compete, they are more likely to live against their opponent and therefore pass on the trait of fitness.
NO - D) Although resources are necessary, large amounts are not as it does not lead to fighting over them (scarcity) bringing us back to the need for competition above.
Hope this helped!