The graphs below show the changes in crab color at one beach. Which statement best explains the change in the number of light tan and dark tan crabs from 1950 to 1990?
a
Both light tan and dark tan body color provided an advantage to the crabs, regardless of their environment or habitat.
b
Either light tan or dark tan body color, but not both colors, provided an advantage to the crabs, regardless of their environment or habitat.
c
Both light tan and dark tan body color provided an advantage to the crabs on this beach, but not necessarily in other crab habitats.
d
Light tan body color provided an advantage over dark tan body color on this beach, but not necessarily in other crab habitats.

Astudent from one of the research labs is having trouble preparing a slide for examination and photographing. the bacterial slide that he has brought to you was prepared using a commercially purchased stain. he has asked for your in determining what he is doing wrong so that he can change the lab protocols and continue on with his project. after examining the slide under oil immersion, you determine that no bacteria are present even though the student is able to show you the culture he used to make that slide that has visible growth in the liquid medium. which of the following statements does not explain the fact that there are no bacteria present on the student’s slide? by not allowing a glass slide to completely air dry before heat fixation, the flame will cause the surrounding water to boil and this will damage the bacterial cell. overheating during the fixation step boiled the water within the bacterial cells and resulted in the cells bursting. insufficient heating of the slide did not drive out the thin layer of water and this resulted in minimal bonding between the bacteria and the glass slide. rinsing with alcohol during the washing step stripped the bacteria off the glass slide. rinsing with alcohol during the washing step stripped the bacteria off the glass slide.