New Words：

bark [bɑ:k] n. 树皮
rough [rʌf] adj. 粗糙的；不平滑的
smooth [smu:ð] adj. 光滑的；平整的

Sample Sentences：

Those trees have very beautiful white bark.
The dog barked when the stranger came near.

The bus went up and down on the rough road.
He felt the rough bark of the tree with his hand.

Her skin is as smooth as silk.
The path through life is not always smooth or easy.

New Words：

rub [rʌb] v. 擦, 摩擦, 搓
microscope ['maikrəskəup] n. 显微镜

Sample Sentences：

I rubbed the window with a cloth.
He rubbed his hands to keep them warm.
Put the paper against the tree, then rub the crayon over it.
The microscope magnified the object 100 times.
They are looking at the blood samples under the microscope.

New Words：

research [ˈriˌsɜrtʃ]
n.研究, 调查
v.研究, 调查

Sample Sentences：

When he left I carried on his research.
He needs to research about the coffee market.
It is important to keep in touch with the latest research.
I've done some research to find out the cheapest way of travelling there.

New Words：

biology [bai'ɔlədʒi] n. 生物学
biologist [bai'ɔlədʒist] n. 生物学家
biological [.baiə'lɔdʒikəl] adj. 生物的；生物学的

Sample Sentences：

Mary is a biologist. She studies biology.
Man is in the highest link of the biological chain.
We do interesting experiments in the Biology classes.
He studied chemistry and then switched to biology.

research [ˈriˌsɜrtʃ]
n.研究, 调查
v.研究, 调查

New Words：

laboratory [ˈlæbrəˌtɔri] n. 实验室

Sample Sentences：

The school has a large biological laboratory.
The students will have an experiment in the laboratory tomorrow.
Our professor usually works in the laboratory doing his research.

biological [.baiə'lɔdʒikəl] adj. 生物的；生物学的
research [ˈriˌsɜrtʃ]
n.研究, 调查
v.研究, 调查