问题 单项选择题

光滑面菌斑属于()

A.龈上菌斑

B.龈下菌斑

C.附着菌斑

D.非附着菌斑

E.获得性菌斑

答案

参考答案:A

解析:菌斑根据其所处的部位分为:①龈上菌斑:即位于龈缘上方或修复体冠部的菌斑,包括光滑面菌斑、点隙裂沟菌斑;②龈下菌斑:即位于龈缘下方的菌斑,包括附着菌斑和非附着菌斑。因此,本题答案应选A。

阅读理解

阅读理解

     Camels are large animals living in dry areas. There are two species of camels: the Arabian camel

with a single hump from the dry desert, and the Bactrian camel with two humps from Centraland East

Asia. Camels are over 7 feet tall and weigh over 1,600 pounds. They will live up to 40 to 50 years .

Most camels are domesticated(驯化)and fed by people. Camels are plant-eaters.

     Camels are very strong animals with wide, padded feet. They have thick leathery pads on their knees

and chest. Camels have nostrils(鼻孔)that can open and close, protecting them from the desert

environment. Bushy eyebrows and two rows of long eyelashes protect their eyes from sand. Their mouth

is extremely tough, allowing camels to eat thorny(带刺的)desert plants. Their widened feet help them

move without sinking into the sand. Their thick coats reflect sunlight, and also protect them from the

intense heat from desert sand. Their long legs help by keeping them further from the hot ground.

     Camels can go without food and water for 3 to 4 days. They do not store water in their humps as is

commonly believed. The humps are actually a container of fat. Camels are incredibly(难以置信)

well-adapted to their environment. When conditions heat up, camels can increase their own body

temperature, which prevents sweating and therefore water loss. They may not sweat at all during the day.

     Camels are sometimes called "ships of the desert" because people ride them around the hot, dry

deserts of the world. However, the number of camels is becoming smaller for various reasons.

1. According to the passage, camels usually live in           .

A. Asia

B. Africa

C. America

D. Australia

2. Paragraph 2 is mainly about           .

A. camels are useful animals

B. camels are clever animals

C. camels' body structure and function

D. camels' characteristics and habits

3. The reason why camels lose little water in deserts is that they           .

A. get water from green foods

B. can adjust their temperature

C. store enough water in the humps

D. can manage without water

4. What will the author probably talk about following the last paragraph?

A. Ways to protect camels.

B. Habitats of camels.

C. Reasons for raising camels.

D. Functions of camels.

单项选择题