The history of modern water pollution goes 【C1】______ to February 20, 1931, when Mrs. Murp

hy 【C2】______ over her backyard fence and said to Mrs. Holbrook, "You 【C3】______ those shirts white？" Mrs. Holbrook was 【C4】______ to admit they were as white as she could get them 【C5】______ that ordinary soap.

"What you should use is this Formula Cake Soap which 【C6】______ against the dull grey look that the family wash 【C7】______ had."

Doubtful 【C8】______ adventurous, Mrs. Holbrook tried the Formula soap, 【C9】______ did take the grey out of her husband's shorts. But what she didn't know was that the water eventually 【C10】______ into the Blue Sky River, killing two fish.

Three years later, Mrs. Murphy was 【C11】______ her shirts and Mrs. Holbrook said, "How did you ever get your collars so 【C12】______ , surely not with Formula？"

"Not ordinary Formula. But I did with Super Fortified Formula. You see, it attacks dirt and destroys it. Here, try some 【C13】______ your shirts. "

Mrs. Holbrook 【C14】______ and discovered her husband's shirt collars turned pure white. What she could not possibly know was that it turned the river water pure white as 【C15】______ .

Six months later, the Blue Sky River was 【C16】______ a health hazard. One day as Mr. Holbrook was walking home from work, he accidentally 【C17】______ the Blue Sky River, swallowed a 【C18】______ of water and died immediately. At the funeral service the minister said, "You can say anything you want about Holbrook, but no one can 【C19】______ he had the 【C20】______ shirts in town."

【C1】

A．straight

B．down

C．off

D．back