In the 1900s, were based in north america, while were based in europe.

   The correct answer is :  Comparative biologists were based in North America, while ethologists were based in Europe.

Explanation:  Comparative biologists formulate hypotheses and in some cases predictions from an existing body and then test them by means of experiments.

Ethologists study the behavior of animals in their natural environment. The etiology is a branch of zoology.

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abraham lincoln  (february 12, 1809  – april 15, 1865) was an american statesman, politician, and lawyer who served as the 16th  president of the united states  from 1861 until  his assassination  in april 1865. lincoln led the nation through the  american civil war, its bloodiest war and its greatest moral, constitutional, and political crisis.[2][3]  he preserved the  union,  abolished slavery, strengthened the  federal government, and modernized  the u.s. economy.