对于大面积的土石方估算常用()。

A、等高线法

B、断面法

C、方格网法

D、透明方格纸法

Passage1

Questions 1 to 5 are based on the followingpassage.

I have come for a visit to an elementary classroomfor six- to nine-year-olds. Mystrongest impressionof this classroomis the purposefulness of the children in theircooperative efforts.

As Isettle in to observe for the morning, I begin to sense that, for these children, relatingto each other and working are a unified(一致的) experience.

The children's voices are low, and Ican only overhear (偶尔听到) the directedconversation of the children at the table closest to me. I realize that the way the children usetheir voices contributes to the atmosphere of respect and purposefulness in this elementaryclassroom.

I hear one of the four boys next to me announce "200-pound explosive shells”.He ispointing to a picture in one of the opened books on the table in front of him. “Did anything blow up?" one of the boys asks. All the boys look over at the opened book Two of the fourboys are taking notes. A third one is making a complicated pencil drawing from an illof a particularmodel of train. The fourth boy is using graph paper（方格纸）to compute amath problem.

A few feetaway from me, three children are sticking pins into holes on a poster boardmap of Europe. The pins have tiny red. labels attachedwith the names of countrieson them.“AIbania," I overhear one boy say as he reads a label to his working partners and puts it onthe map.

Just beyond these children, five others have newspapers spread over a large table. One ofthe children walks over to the assistant, carrying what looks to meto be the sports section ofone of the newspapers. These children must be following basketballscores or related sportsstatistics.

The only other table on which I can see the work clearly is next to this newspaper" table.This is a small table with only two children. Their books are standing up on end so that I cansee, even across the room, that they are doing a report on jungle birds and animals.

Such is an elementary class! The children are ell-occupied, learning, concentrated,interested, and purposeful Every subject area but music is covered. This classroomis sodifferent from my own elementary shooling. I want to know how this particularteacher helpsto facilitatethis outcome with this particulargroup of children.

What strongly impresses the authorin the elementary classroom?