A sample of plutonium-239 decays from 341.92 kilograms to 42.74 kilograms. This is 1/8 the original sample. How many half-lives have passed?

Which supports the idea that birds and butterflies both have wings but they do not have a common ancestor with wings? a. the wings are analogous structures that evolved differently and do not have a similar internal structure. b. the wings are homologous structures that evolved differently and do not have a similar internal structure. c. wings of birds are vestigial structures, but the wing structures of bats are not vestigial. d. wings of bats are vestigial structures, but the wing structures of birds are not vestigial

Which of the following would be an accurate picture of the earth during the summer time of the northern hemisphere?

Which statement best describes the he properties of iconic compounds ?