某二元酸（化学式用H₂A表示）在水中的电离方程式是：H₂A＝H⁺+HA^- HA^-H⁺+A^2-

回答下列问题：

（1）Na₂A溶液显____________（填“酸性”，“中性”，或“碱性”）。理由是__________________________________（用离子方程式表示）

（2）在0．1mol·L^-1的Na₂A溶液中，下列微粒浓度关系式正确的是__________

A、c(A^2-) +c(HA^-)+c(H₂A) ＝0．1mol·L^-1

B、c(OH^-) ＝c(H⁺) +c(HA^-)

C、c(Na⁺)+ c(H⁺) ＝c(OH^-)+c(HA^-)+c(A^2-)

D、c(Na⁺) ＝2c(A^2-) +2c(HA^-)

（3）已知0．1mol·L^-1NaHA溶液的pH=2，则0．1mol·L^-1 H₂A溶液中c(A^2-)可能是_______0．01 mol·L^-1

（填“＜”，“＞”，或“＝”）。

A proven method for effective textbook reading is the SQ3R method developed by Francis Robinson. The first step is to survey (the S step) the chapter by reading the title, introduction, section headings, summary and by studying any graphs, tables, illustrations or charts. The purpose of this step is to get an overview of the chapter so that you will know before you read what it will be about. In the second step (the Q step), for each section you ask yourself questions such as "What do I already know about this topic" and "What do I want to know" In this step you also take the section heading and turn it into a question. This step gives you a purpose for reading the section. The third step (the first of the 3 R’s) is to read to find the answer to your questions. Then at the end of each section, before going on to the next section, you recite (the second of the 3 R’s) the answers to the questions that you formed in the question step. When you recite you should say the information you want to learn out loud in your own words. The fifth step is done after you have completed steps 2, 3 and 4 for each section. You review (the last of the 3 R’s) the entire chapter. The review is done much as the survey was in the first step. As you review, hold a mental conversation with yourself as you recite the information you selected as important to learn. The mental conversation could take the form of asking and answering the questions fromed from the headings or reading the summary, which lists the main ideas in the chapter, and trying to fill in the details for each main idea.

The passage implies that the SQ3R method（）

A. needs to be proven

B. leaves much to he desired

C. turns out to be practicable

D. cannot be used by every reader