Which of the following best describes the biological role of the lac operon? a) it prevents other sugars from being metabolized until all available lactose has been used. b) it ensures that a cell dedicates resources to the production of enzymes involved in lactose metabolism only when lactose is available in the environment. c) it ensures that a cell produces enzymes involved in lactose metabolism in a constitutive manner. d) it ensures that bacterial cells produce lactose only when no other food sources are available.

On a recent expedition to a remote region of northern canada, scientists uncovered skeletal remains from about 100,000 years ago. surprisingly, all the skeletal remains, which included many species from differing biological families and spanned about two thousand years, showed evidence of experiencing temperatures in excess of 1000 degrees fahrenheit (or 538 degrees celsius). which of the following, if true, best explains the apparent paradox between the cold environment and the evidence of the bones experiencing hot temperatures? (a) chemical changes that naturally occur during the process of decay in only one north canadian species produce the same evidence of the species' skeletons being exposed to hot temperatures as the expedition scientists found. (b) a little over 103,000 years ago, a large fire is known to have occurred in northern canada. (c) strong evidence exists that as early as 70,000 years ago, homo sapiens around the world relied heavily on fire to cook animals. (d) in the same expedition and in roughly the same layer of excavation, scientists found rudimentary wood cutting and hunting tools used by early humans.