21．下列波長中屬于可見光的有（          ）

A．100nm                                                      B．240nm

C．460nm                                                      D．580nm

E．700nm

22．下列屬于完全變態(tài)的昆蟲有（          ）

A．衣魚                                                        B．蟑螂

C．煙草甲                                                     D．檔案竊蠹

E．黑皮蠹

23．下列物質(zhì)中，屬于一次污染物的有（          ）

A．SO₃                                                          B．H₂SO₄

C．SO₂                                                          D．Cl₂

E．H₂S

24．復(fù)寫紙色層漿料的組成有（          ）

A．蠟                                                            B．防腐劑

C．油                                                            D．色素

E．粘合劑

25．植物纖維主要的化學(xué)成分有（          ）

A．葡萄糖                                                     B．半纖維素

C．木素                                                        D．纖維素

E．木糖