单项选择题

It was late on an August afternoon, the air hot and heavy like it usually was in the rainy season. Earlier we’d seen some thunderheads near the Burnt Spring Hills, but they’d passed way up to the north. I’d mostly finished my chores for the day and was heading down to the pasture with my brother, Buster, and my sister, Helen, to bring the cows in for their milking. But when we got there, those girls were acting all bothered. Instead of milling around at the gate, like they usually did at milking time, they were standing stiff-legged and straight-tailed, twitching their heads around, listening.
Buster and Helen looked up at me, and without a word, I knelt down and pressed my ear to the hard-packed dirt. There was a rumbling, so faint and low that you felt it more than you heard it. Then I knew what the cows knew—a flash flood was coming.
I figured we best bolt, too, so I grabbed Helen and Buster by the hand. By then I could feel the ground rumbling through my shoes. I saw the first water sluicing through the lowest part of the pasture, and I knew we didn’t have time to make it to higher ground ourselves. In the middle of the field was an old cottonwood tree, broad-branched and gnarled, and we ran for that.
Helen stumbled, so Buster grabbed her other hand, and we lifted her off the ground and carried her between us as we ran. When we reached the cottonwood, I pushed Buster up to the lowest branch, and he pulled Helen into the tree behind him. I shimmied up and wrapped my arms around Helen just as a wall of water, about six feet high and pushing rocks and tree limbs in front of it, slammed into the cottonwood, dousing all three of us. The tree shuddered and bent over so far that you could hear wood cracking, and some lower branches were torn off. I feared it might be uprooted, but the cottonwood held fast and so did we, our arms locked as a great rush of caramel-colored water, filled with bits of wood and the occasional matted gopher and tangle of snakes, surged beneath us, spreading out across the lowland and seeking its level.
We just sat there in that cottonwood tree watching for about an hour. The sun started to set over the Burnt Spring Hills, turning the high clouds crimson and sending long purple shadows eastward. The water was still flowing beneath us, and Helen said her arms were getting tired. She was only seven and was afraid she couldn’t hold on much longer.
Buster, who was nine, was perched up in the big fork of the tree. I was ten, the oldest, and I took charge, telling Buster to trade places with Helen so she could sit upright without having to cling too hard. A little while later, it got dark, but a bright moon came out and we could see just fine. From time to time we all switched places so no one’s arms would wear out. The bark was chafing my thighs, and Helen’s, too. About halfway through the night, Helen’s voice started getting weak.
"I can’t hold on any longer," she said.
"Yes, you can," I told her. "You can because you have to. " We were going to make it, I told them. I knew we would make it because I could see it in my mind. I could see us walking up the hill to the house tomorrow morning, and I could see Mom and Dad running out. It would happen—but it was up to us to make it happen.
To keep Helen and Buster from drifting off to sleep and falling out of the cottonwood, I grilled them on their multiplication tables. When we’d run through those, I went on to presidents and state capitals, then word definitions, word rhymes, and whatever else I could come up with, snapping at them if their voices faltered, and that was how I kept Helen and Buster awake through the night.
By first light, you could see that the water still covered the ground. In most places, a flash flood drained away after a couple of hours, but the pasture was in bottomland near the river, and sometimes the water remained for days. But it had stopped moving and had begun seeping down through the sinkholes and mudflats.
"We made it," I said.
I figured it would be safe to wade through the water, so we scrambled out of the cottonwood tree. We were so stiff from holding on all night that our joints could scarcely move, and the mud kept sucking at our shoes, but we got to dry land as the sun was coming up and climbed the hill to the house just the way I had seen it.
What did "I" NOT do to keep Buster and Helen safe