A uranium-235 sample starts with 200 atoms, and 700 million years later, there are 100 atoms. What is the half-life of uranium-235?
A. 350 million years
B. 235 years
C. 100 years
D. 700 million years

How do plants obtain more sunlight a.) they lean towards the light b.)they grow straight up c.) they only live in sunny areas, like the tropics d.) they stay low to the ground

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.

Science which of the following is an example of a cyclic behavior that is seasonal? i think the answer is d, i just need to double check : ). a. running from predators. b. searching for water. c. hunting at night. d. migrating for warmth. ***