给玻片标本染色时，最合理的操作是（  ）

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    Walt Whitman was a famous American poet (诗人). He was born 1 Mary 31, 1819, in Long Island. There were nine2 in his family, and he was the second. 3 he was four years old, his family moved to Brooklyn because his family was too poor. His childhood was restless (不安宁的) and unhappy. 4 the age of 11, he left school. Then he began to 5 a job to help his family. As a young man, Whitman 6 a school teacher, a printer and a newspaper reporter. He was 7 years old when he published his first book of poetry (诗集) in 1855. He 8 itLeaves of Grass. It 9 only twelve poems. The new form of his poetry 10 many people. Whitman was poor and weak during the last years of his life. He died in 1892.