What are the Dow and the S&P 500?
averages of stocks and bonds that are traded often
cumulative records of all stocks sold on the NYSE and other major exchanges
indexes that show the performance of limited but representative stocks
indexes that track the sales of all the stocks and bonds in the United States

indexes that show the performance of limited but representative stocks

Explanation:

The Dow has changed the companies it tracks over the years to make sure they remain representative of the market as a whole. The S&P reports mainly stocks listed on the NYSE, but some of its stocks are traded on the NASDAQ and the OTC markets.

answer; maintain a safe following distance;

ans.

heterothermic organisms include those organisms that can switch between homeothermic (having body temperature higher than environment) and poikilothermic (having variation in internal body temperature) strategies.

some migratory birds show heterothermy as they decrease their metabolic rate during cold nights to keep their body temperature low. drop in metabolic rate allows increase in production efficiency of birds that reduces the internal body temperature to make it equal to external cold temperature during cold nights.

thus, the correct answer is 'birds allow their temperature drop in order to increase their production efficiency.'