The roads are lined________trees，which have b...

The roads are lined________trees，which have been planted to hold________the strong winds from the north.

A. along; to             B．on；up          C．in；against           D．with；back

高二英语单项填空简单题查看答案及解析

The trees ___________ down in the storm have been moved off the road.

A. being blown           B. blown

C. having been blown                  D. blowing

高二英语单项填空中等难度题查看答案及解析

Since the forest has been destroyed by a big fire, a large ______ of trees ______ to be planted on the mountain．

A．number; has                          B．amount; has

C．quantity; have                           D．sum; have

高二英语单项填空困难题查看答案及解析

.People have planted a great many trees in order to _____ wind and sand in the desert.

高二英语单项填空简单题查看答案及解析

A tree was planted along the road 　　 . Choose the one that is not proper for the blank.

A.every two meters B.every second meter

C.every other meter D.every the second meter

高二英语单项填空中等难度题查看答案及解析

People have planted a great many trees in order to ________ wind and sand in the desert.

A．hold down        B．hold up          C．hold back        D．hold out

高二英语单项填空中等难度题查看答案及解析

We have planted a lot of trees to _____ wind and sand in the desert．

A．hold up                                               B．hold down

C．hold back                                            D．hold out

高二英语单项填空中等难度题查看答案及解析

There are trees and flowers along both sides of the road______ our school.

高二英语单项填空中等难度题查看答案及解析

Have you ever wondered why the roots of the plants always know which way to grow—into the soil but not above it? Some British scientists have recently solved this mystery.

It turns out that roots have special hairs that tie them into the soil and help them grow their way past obstacles, a team at the John Inners Center in Norwich reports in the February 29 issue of Journal Science.

“The key is in the fuzzy(有绒毛的)coat of hairs on the roots of plants,” says professor Liam Dolan. “We have found a growth control system that enables these hairs to find their way and to become longer when their path is clear.”

Root hairs explore the soil in much the same way a person would feel their way in the dark. If they come across an obstacle, they make their way around until they can continue growing in an opening. In the meantime, the plant is held in place as the hairs grip(紧紧抓住)the soil.

The hairs are guided by a clever chemical trick. A protein(蛋白质) at the tip of the root hairs called RHD2 helps them to take calcium(钙) from the soil. Calcium makes the hairs grow, and produce more RHD2, and take more calcium.

But when an obstacle blocks the hair’s path, or the hair reaches the surface of the soil, the cycle is broken and growth starts in another direction.

This system gives plants the flexibility to explore a complex environment and to live in even the most unpromising soils, says Dolan.

In poor soils such as in parts of Australia and Africa, native plants have adapted by producing enormous numbers of root hairs. A better understanding of this adaptation will allow scientists to develop hairy rooted crops that can grow in unfriendly environments.

According to Dolan, “Research in the John Inners Center is taking a breeding approach to increase hair length in wheat but it will be some time before new cultivars(栽培变种) are developed.”

1.The passage is mainly about _______.

2.How does the circle work?

3.We can infer from the last paragraph that ________.

高二英语阅读理解困难题查看答案及解析

One generation plants the trees under________shade another generation rests.

A．which            B．where            C．whose            D．what

高二英语单项填空中等难度题查看答案及解析