Why did president Pierce get credit for for the Ostend Manifesto and the Gadsden Purchase?

Explanation:  communication from three U.S. diplomats to Secretary of State ... U.S. minister to Spain, failed in his mission to secure the purchase of Cuba (1853), Marcy ... The resulting diplomatic statement, the Ostend Manifesto

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.

which statement best describes the relationship between the fourteenth amendment and the african american civil rights movement?