Two forces f1 and f2 act on a particle. as a result the speed of the particle increases. which one of the following is not possible? choose one answer. a. the work done by f1 is positive, and the work done by f2 is zero b. the work done by each force is positive. c. the work done by f1 is positive, and the work done by f2 is negative. d. the work done by each force is negative. e. the work done by f1 is zero, and the work done by f2 is positive.

Which of the following are the functions of the skeletal system? blood cell production in soft marrow tissues and mineral reserves largest organ of the body for defense and support vitamin d production and pumping blood through vessels voluntary movement and contractile movement

Over the past 60 years, many amphibian species have experienced significant population declines and some species have become extinct. scientists suspected that local human activities such as the destruction of wetlands, regional pollution, and deforestation were the main reasons for these losses. however, research over the past 20 years reveals significant amphibian population declines in protected areas of the world, such as nature preserves and parks. these global declines suggest widespread problems including increased ultraviolet radiation, acid rain, and disease. in switzerland, for example, 14 of the 20 native amphibian species are threatened with extinction. chytridiomycosis is a fungal disease first identified in 1998 as a cause of massive amphibian deaths. in some severely impacted populations, a few individuals have survived, perhaps because of some natural resistance. if these resistant individuals continue to survive and prosper, new resistant populations might emerge. this would be an example of the founder effect artificial selection genetic drift natural selection sexual selection

Most of the fossils found in virginia are in the coastal plain, valley, ridge, and appalachian plateau regions, best suggesting that these geographic provinces a) were once covered by seawater. b) are the oldest parts of virginia. c) have a great deal of karst topography. d) have large amounts of sedimentary rock.