反向市场牛市套利的市场特征有（）。 A.现货价格高于期货价格 B.只要价差扩大，就可

确定病原微生物基因在感染中的作用需满足分子Koch假设，以下选项属于Koch假设的是（）

A.特异性灭活可疑的毒力基因或基因群导致毒力降低

B.基因的野生型拷贝替换突变型拷贝后，原菌的致病性完全消失

C.能建立致病基因的动物模型

D.质粒载体在研究的细菌中复制

E.研究的表型或特征与致病菌株有关，与非致病菌株无关

阅读下列材料, 从所给的四个选项(A、Ｂ、Ｃ、Ｄ) 中，选出符合各小题要求的最佳选项，并在答题卡上将该项涂黑。

The people below are needed to take part in a sport. After the description of these people, there is information about four sports(A-D). Decide which sport would be most suitable for the person mentioned in questions 58-61 and then mark the correct letter(A-D) on your answer sheet.

小题1:Bob is a very active man. He is very strong and healthy. He’d like to take part in an exciting sport. But he is afraid of water.

小题2:Simon is very fat. He would like to lose his weight. But he is not interested in double quick and excitement activity. He enjoys water sports.

小题3:Mathew hates to take part in the violent sports. He is in poor health. He wants to build up his body.

小题4:Jack is brave and risky and a good swimmer. He enjoys water game. He looks for excitement with his friend when they are on holiday.

A．Hiking is a great way to travel. You will get close to nature and take exercise at the same time. Hiking is easy to do and doesn’t have to be very expensive. You can hike close to home or travel to other places. The basic equipment you need for hiking is simple: good shoes, clothes and a backpack. You can hike in the mountains, in a forest or along a river. You can also go for a hike in the city. Hiking is fun and exciting, but you shouldn’t forget safety.

B．Rafting is a good way to experience nature. If you want a normal rafting trip, choose a quiet stream or river that is wide and has few fallen trees or rocks. If you are looking for more excitement you may want to try whitewater rafting. You should always think about your safety and wear good clothes. You also need to learn the basic skills of rafting, such as how to handle the raft, how to paddle and how to get in and out of the raft. You should not go rafting unless you know how to swim, and you should always wear a life jacket.

C．Swimming is a good way for swim lovers. You can reduce your weight and become slim by swimming. You can train your willpower and increase your energy of your lung. You can swim in the swimming pool, in the lake, in the river or even in the sea.

D．Long running is a good sport, for example, Marathom is very popular with young people especially people with strong body and will. If you have hypertension or heart disease, perhaps, it is not suitable for you.

柴油机气缸盖要有足够强度和刚度，防止气缸盖因应力过大而损坏或因变形而漏泄。

鲜生姜、鲜石斛等药物易发生的变异现象是（）

A.虫蛀

B.霉变

C.粘连

D.变色

E.腐烂

屋面水平出入口的附加防水层不宜空铺或点粘，平面部分宜铺至踏步下，与防水层之间应满粘。( )