题目内容：

阅读下面材料，根据其内容和所给段落开头语续写两段，使之构成一篇完整的短文。续写的词数应为150左右。

Rebecca stretched her tired back. “That’s the last seedling(种树苗), Pa. Have we planted enough?” Pa walked to the end of the row of cottonwood seedlings. “No,” he said. “We have to plant trees all the way to that rock over there. We’ll need about twenty more seedlings.”

“I’ll get the seedlings,” offered Rebecca. She longed to cool her feet in the shallow river running through the cotton field. “You’d better let me go,” teased her twin brother, William. “There are dangers all over this prairie(牧场）. “You may both go,” said Pa.

They went across the shallow river to a sandbar where small cottonwood seedlings grew. Gently, they pulled the seedlings from the sand. “There! That’s twenty, with a few to spare.” said Rebecca. “OK,” said William. He led the way to the riverbank, then stopped.

“Look! There’s the dugout(防空壕）we lived in when we moved here last year.” He pointed to a hole in the grassy river bank. “Come on, let’s go inside.” “No,” Rebecca said. “Then you start back.” said William, handing the seedlings to Rebecca. I’ll catch up.” He ran to the dugout and stepped inside.

Rebecca tied the seedlings into her long apron(围裙）and began to walk. Suddenly she froze in her tracks. A huge prairie rattlesnake(响尾蛇）moved along the river bank. It stopped right in front of the dugout and lay still, coiled up on the warm sunny bank. “William!” Rebecca shouted. “Don’t come out!”

“Huh?” William's face appeared at a tiny window beside the door of the dugout. Rebecca pointed toward the rattler. William's face paled when he saw the snake blocking the doorway. He turned desperate eyes toward Rebecca, then he glanced behind himself.

Rebecca’s mind raced, trying to think of a way to get William out of there. An idea popped into her head. It was their only hope. It was risky, but it was the only hope. “Don’t move,” she said to William in a soft voice. “When I say NOW, you run out of there as fast as you can.” Rebecca removed the skirt-like petticoat(衬裙）from beneath her dress, then dipped it into the river. She squeezed out some of the water, then climbed to the top of the bank, directly above the dugout’s opening.

Paragraph 1:

"Get ready to run, William,” she said, keeping an eye on the motionless snake.

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Paragraph 2:

"Are you OK?" he asked, breathing heavily. Rebecca nodded.

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