对湿陷性土采用垫层法处理时，回填材料应尽量采用（）A．不含有机质等有害杂物的建筑垃圾

一种证券或组合在均值标准差平面上的位置完全由该证券或组合的期望收益率和标准差所确定。 ( )

阅读理解

     Honey from the African forest is not only a kind of natural sugar, it is also delicious.

     Most people, and many animals, like eating it. However, the only way for them to get that

honey is to find a wild bees' nest and take the honey from it. Often, these nests are high up in

trees, and it is difficult to find them. In parts of Africa, though, people and animals looking for

honey have a strange and unexpected helper - a little bird called a honey guide.

      The honey guide does not actually like honey, but it does like the wax in the beehives (蜂房).

The little bird cannot reach this wax, which is deep inside the bees' nest. So, when it finds a suitable

nest, it looks for someone to help it. The honey guide gives a loud cry that attracts the attention of

both passing animals and people. Once it has their attention, it flies through the forest, waiting from

time to time for the curious animal or person as it leads them to the nest. When they finally arrive at

the nest, the follower reaches in to get at the delicious honey as the bird patiently waits and watches.

Some of the honey, and the wax, always falls to the ground, and this is when the honey guide takes

its share.

     Scientists do not know why the honey guide likes eating the wax, but it is very determined in its

efforts to get it. The birds seem to be able to smell wax from a long distance away. They will quickly

arrive whenever a beekeeper is taking honey from his beehives, and will even enter churches when

beeswax candles are being lit.

1. Why is it difficult to find a wild bees' nest?

A. It's small in size.

B. It's hidden in trees.

C. It's covered with wax.

D. It's hard to recognize.

2. What do the words "the follower" in Paragraph 2 refer to?

A. A bee.

B. A bird.

C. A honey seeker.

D. A beekeeper.

3. The honey guide is special in the way              .

A. it gets its food

B. it goes to church

C. it sings in the forest

D. it reaches into bees' nests

4. What can be the best title for the text?

A. Wild Bees

B. Wax and Honey

C. Beekeeping in Africa

D. Honey-Lover's Helper

某研究者欲了解2007年某地成年男性的高血压患病情况，抽样调查了200名当地的成年男性，测量并记录其收缩压和舒张压值。

描述该资料的变异程度，宜选用（）。

A.极差

B.四分位数间距

C.方差

D.标准差

E.变异系数

以下属于福建名菜的是（）

A.盐焗鸡

B.冰糖甲鱼

C.佛跳墙

D.干菜焖肉

砂浆强度等级以边长7.07cm立方体试件按标准条件养护多少天的抗压强度确定

A．7d
B．10d
C．15d D．28d