Passage 1
Fall is staggering in, right on schedule, with its baggage of chilly nights, spectacular, heart-stoppingly beautiful leaves. People will travel up and down the East Coast just to stare at it—a whole season of leaves.
Where do the colors come from? Sunlight rules most living things with its golden edicts. When the days begin to shorten, a tree reconsiders its leaves. All summer it feeds them so they can process sunlight, but in the dog days of summer the tree begins pulling nutrients back into its trunk and roots, reduces and gradually chokes off its leaves. A dry layer of cells forms at the leaves’ slender stems, then scars over. Undernourished, the leaves stop producing the pigment chlorophyll, and photosynthesis ceases. Animals can migrate, hibernate, or store food to prepare for winter. But where can a tree go? It survives by dropping its leaves, and by the end of autumn only a few fragile threads of fluid-carrying xylem hold leaves to their stems.
A turning leaf stays partly green at first, then reveals spots of yellow and red as the chlorophyll gradually breaks down. Dark green seems to stay longest in the veins. During the summer, chlorophyll dissolves in the heat and light, but it is also being steadily replaced. In the fall, on the other hand, no new pigment is produced, and so we notice the other colors that were always there, right in the leaf, although chlorophyll’s shocking green hid them from view. With their camouflage gone, we see these colors for the first time all year, but they were always there, hidden like a vivid secret beneath the hot glowing greens of summer.
An odd feature of the colors is that they don’t seem to have any special purpose. Animals and flowers color for a reason—adaptation to their environment—but there is no adaptive reason for leaves to color so beautifully in the fall any more than there is for the sky or ocean to be blue. It’s just one of the haphazard marvels the planet presents every year. We find the sizzling colors thrilling, and in a sense they cheat us. Colored like living things, they signal death and disintegration. In time, they will become fragile and, like the body, return to dust. They are as we hope our own fate will be when we die: Not to vanish, just to sublime from one beautiful state into another. Though leaves lose their green life, they bloom with urgent colors, as the woods grow mummified day by day, and Nature becomes more carnal, mute, and radiant...
The signal for a tree to begin its preparation for winter is when ________.
文章第一段第一句提到“Fall is staggering in, right on schedule, with its baggage of chilly nights, spectacular, heart-stoppingly beautiful leaves.”。由此可知，秋天来了之后，夜里开始变凉，树也开始落叶。 这便是树要准备过冬的标志。故选A。
According to the passage, the leaves’ color changing process should be traced back to ________.
文章第二段第三句提到“All summer it feeds them so they can process sunlight, but in the dog days of summer the tree begins pulling nutrients back into its trunk and roots, reduces and gradually chokes off its leaves.”。由此可知，在炎热的盛夏时节，树就开始把营养物质运向枝干和根部，慢慢抑制叶的生长。故选B。
We just see green in summer because ________.
文章第三段第三句提到“During the summer, chlorophyll dissolves in the heat and light, but it is also being steadily replaced.”。夏天，叶绿素在光和热下很容易分解，但也能够很稳定地被替换。由此可知，夏 天树绿的原因在于叶绿素足够多，所以都是绿色的。故选D。
In the last paragraph, the beautifully colored leaves are compared to ________.
文章最后一段倒数第三、四句提到“In time, they will become fragile and, like the body, return to dust. They are as we hope our own fate will be when we die...”，由此可知，树叶凋零的过程被比作了人死亡的过 程。故选C。
Which of the following will the author agree?
文章最后一段第二句提到“...there is no adaptive reason for leaves to color so beautifully in the fall any more than there is for the sky or ocean to be blue”。由此可知，树叶颜色变化是为了适应环境。故选C。