Correct Response: C. Keeping the sash lowered is necessary in order to contain fumes produced by the reaction within the exhaust hood. A is incorrect because using Bunsen burners within the fume exhaust hood does not present a safety hazard and is a necessary part of performing the experiment. B is incorrect because turning off the fan would prevent the removal of undesired fumes by the exhaust hood (the exhaust hood cannot work when it is off). D is incorrect because stepping away from the fume exhaust hood would prevent the student from being able to manipulate the experiment within the exhaust hood and is not a necessary method for avoiding exposure to fumes.
