[填空题]_____ have started early this summer.

[填空题]_____ have started early this summer.

[简答题]No sooner______(她同意嫁给他)than she started to have terrible doubts．

[单项选择]The young pioneers started off early ______ the ______lamb.
A. to search for, missed
B. to search, missing
C. to search, missed
D. to search for, missing

[单项选择]In the early 1900s, （　） started the first chain operation in the United States.
A. Kemmons Wilson
B. Ellsworth Statler
C. Conrad Hilton
D. Thomas Cook

[单项选择] The fires were thought to have been started
A. purposefully.
B. accidentally.
C. on the Mexican border.
D. in southern California.

[单项选择]Since the early 1980s, scientists have revealed some 40 human genes involved in cancer. These genes are essential for normal growth, but can be subverted to cause a tumor.
Dr. Jorge Yunis of the University of Minnesota Medical School in Minneapolis has found that 70 percent of oncogenes, or cancer-causing genes, are located near inherited weak points on chromosomes(染色体). Varying from individual to individual, vulnerable to chemical carcinogens(致癌剂) ,X rays and other cancer-inducing agents.
"If a chromosome snaps apart in the immediate vicinity of an oncogene," says Yunis, "normal genetic control mechanisms could break down and the stage would be set for the formation of cancer." Younis hag shown that such a sequence occurs at the beginning of numerous leukemias (白血病), lymphomas (淋巴瘤) and some tumors of the lung, colon (结肠) and breast.
Yunis and Other investigators have found that petroleum-based products--notably pesticides and insecticides--damage specific sites on at l
A. harmful to the human body
B. necessary to the human body
C. the elements that form cancer
D. useless to the human body

[填空题]Early men did not have clocks. They were told time 76. ______
by the sun and shadows of trees. At first time, they used 77. ______
sticks placed in the ground instead trees. They made 78. ______
marks in the ground, and the shadows from the sticks told 79. ______
the time of day. Later, men began to use sundials. Some of 80. ______
sundials were boxes with sticks cast a shadow. Men were 81. ______
able to take the sundial box with them. The mark for noon 82. ______
was very important. The sundials always have to face the same 83. ______
way or the time was wrong. Sundials were good only on sunny 84. ______
days, not on cloud days. They were the first kind of clock. 85. ______