根据语境，用方框中所给短语的适当形式填空。（每个短语仅使用一次）

    Frederick Douglass was an escaped slave in the movement that fought to end slavery in the United States. He became a{#blank#}1{#/blank#} voice in the year before the Civil War.

    A few weeks ago, the National Park Service (NPS) {#blank#}2{#/blank#} Douglass's birth and Black History Month with reopening of his home at Cedar Hill, a{#blank#}3{#/blank#}  site in Washington. D.C. The two-story house, which contains many of Douglass's personal possessions, had undergone a three-year {#blank#}4{#/blank#} . (Thanks to the NTS website, however, you don't have to live in the nation's capital to visit it. Take a tour online.)

He was born in Frederick Augustus Washington Bailey to a slave mother and a white father who never knew Douglass grew up to become the first black {#blank#}5{#/blank#} to hold a government office— as US minister and consul general (总领事)to Haiti.

    As a youth, he never went to school. Educating slaves was illegal in the South, so he{#blank#}6{#/blank#}  taught himself to read and write. At 21 years old, he escaped from his slave owner to Massachusetts and changed his last name to Douglass, to hide his identity.

    In the 1850s, Douglass was involved with the Underground Railroad, the system {#blank#}7{#/blank#} up by antislavery groups to bring runaway slaves to the North and Canada. His home in Rochester, N.Y. was near the Canadian border. It became an important station on the {#blank#}8{#/blank#} , housing as many as 11 runaway slaves at a time.

    He died in 1895. In his lifetime, Douglass {#blank#}9{#/blank#}  the end of slavery in 1865 and the adoption of the 15^th Amendment to the US Constitution (美国宪法修正案), which{#blank#}10{#/blank#} African-Americans the right to vote.

Can a precise word total ever be known? No, says Professor David Crystal, known chiefly for his research in English language studies and author of around 100 books on the {#blank#}1{#/blank#}. "It's like asking how many stars there are in the sky. It's impossible to answer," he said.

An easier question to answer, he {#blank#}2{#/blank#}, is the size of the average person's vocabulary. He suggests taking a sample of about 20 or 30 pages from a medium-sized dictionary, which {#blank#}3{#/blank#} about 100,000 entries or 1,000 or 1,500 pages.

Tick off the ones you know and count them. Then {#blank#}4{#/blank#} that by the number of pages and you will discover how many words you know. Most people vastly underestimate their {#blank#}5{#/blank#}.

"Most people know half the words—about 50,000—easily. A reasonably educated person about 75,000 and a really cool, smart person well, maybe all of them but that is rather {#blank#}6{#/blank#}. An ordinary person, one who has not been to university say, would know about 35,000 quite easily."

The formula can be used to calculate the number of words a person uses, but a person's active language will always be less than their {#blank#}7{#/blank#}, the difference being about a third.

Prof Crystal says exposure to reading will obviously expand a person's vocabulary but the level of a person's education does not {#blank#}8{#/blank#} decide things. "A person with a poor education perhaps may not be able to read or read much, but they will know words and may have a very {#blank#}9{#/blank#} vocabulary about pop songs or motorbikes. I've met children that you could {#blank#}10{#/blank#} as having a poor education and they knew hundreds of words about skateboards that you won't find in a dictionary."