Nhận biết (M1)

Among highly social mammals, the company of others of the same species has been seen to blunt stress. To find out whether this so-called social buffering runs in reptiles too, researchers under Iona Brackenridge tracked how wild southern Pacific rattlesnakes (Crotalus helleri) answer stress across three treatments: left alone, given a rope, and given a fellow snake for company. What the team compared was the percentage change from baseline heart rate to peak heart rate in answer to a harmless disturbance, a higher figure marking greater stress.

Which finding, if true, would most directly support the idea that social buffering occurs among C. helleri?

• A.

  Peak heart rates on average ran highest in the snakes left alone, though companioned snakes and rope snakes did not differ in average peak heart rate.

• B.

  Companioned snakes showed both a lower average baseline heart rate and a lower average peak heart rate than snakes left alone or snakes given a rope did.

• C.

  The average percentage change in heart rate ran lower in companioned snakes than in snakes left alone or snakes given a rope.

• D.

  Snakes left alone carried higher average baseline heart rates than snakes in the other treatments, and yet the average percentage change in heart rate came out smaller in them than in companioned snakes.