白细胞减少症是指外周血中白细胞计数持续（） A.9/L B.9/L C.9/L D.

Mulch is a protective cover of material that is spread on top of soil.It is usually made out of organic material, like crop waste.Farmers may keep the remains of maize or other crops on top of the soil.This creates mulch on the soil surface.The plant remains help protect the soil against wind and water damage.Mulching is one of the best things people can do for their plants.It also helps keep the soil from getting dry, and reduces the need for watering plants.It also limits temperature changes in the soil.And it stops unwanted plants, or weeds，from growing.

Organic mulch improves the condition of soil.As the mulch breaks down, it provides material which keeps the soil from getting hard.This improves the growth of roots and increases the movement of water through the soil.It also improves the ability of the soil to hold water. Organic mulch contains nutrients for plants.It also provides a good environment for earthworms and other helpful organisms in the soil.

It is easy to find organic mulch materials.Cut­up leaves and small pieces of tree bark can be used.Grass cuttings are also a good mulch for plants. Mulch from newspapers works well in controlling weeds.

The best time to add mulch depends on your goal.Mulch provides a thick barrier between the soil and the air.This helps to reduce temperature changes in the soil. As a result，mulched soil will be cooler than other soil in the summer.In winter, the mulched soil may not freeze as deeply as other soil.The best time is after the ground has frozen, but before the coldest weather arrives.Spreading mulch before the ground has frozen may attract small animals searching for a warm place to spend the winter.Delaying the spreading should prevent this problem.The animals will probably find another place to live.

小题1:The author tells us the following EXCEPT________.

A．what mulch is and its benefits

B．the best time to add mulch

C．what can be mulched on the soil surface

D．the bad effects of mulch小题2:The following can be used as organic materials to make mulch EXCEPT________.

A．tree barks

B．cut­up leaves

C．grass cuttings

D．plastic小题3:Which of the following is the benefit of mulch?

A．Protecting the soil against wind and water damage.

B．Keeping the soil wet and reducing the need for watering plants.

C．Reducing temperature changes in the soil and stopping unwanted weeds

growing.

D．All of the above.小题4:The main idea of Paragraph 2 is that organic mulch can________.

A．improve the condition of soil

B．improve the ability of the soil to hold water

C．provide a good environment for earthworms

D．improve the growth of roots and increase the movement of water through thesoil

小题5:From the last paragraph, we know ________.

A．the best time to add mulch is in spring and summer

B．the best time to add mulch is after the coldest weather arrives

C．the best time to add mulch depends on weather

D．choosing the best time to add mulch can avoid attracting small animals

中外合资股份有限公司

我国实现现代化最困难的问题是（）

A.市场化

B.工业化

C.信息化

D.农业现代化

某施工单位承包某工程项目，甲乙双方签订的关于工程价款的合同内容有：
(1)建筑安装工程造价660万元，建筑材料及设备费占施工产值的比重为60%。
(2)工程预付款为建筑安装工程造价的20%。工程实施后，工程预付款从未施工工程尚需的主要材料及构件的价值相当于工程预付款数额时起扣，从每次结算工程价款中按材料和设备占施工产值的比重扣抵工程预付款，竣工前全部扣清。
(3)工程进度款逐月计算。
(4)工程保修金为建筑安装工程造价的3%，竣工结算月一次扣留。
(5)材料和设备价差调整按规定进行(按有关规定上半年材料和设备价差上调10%，在6月份一次调增)。
工程各月实际完成产值见下表。

通常工程竣工结算的前提是什么