Facing this 17 , engineers at a Japanese company have developed a thin-film flexible solar panel.
答案：(C) challenge
語意「面對這個『挑戰』」，challenge（挑戰）符合，呼應前文提到矽材料昂貴且面板笨重的問題；strength（優勢）、feature（特色）、reaction（反應）都不合。
本題大考中心未公布逐題答對率，以下不談數據，只談觀念。
四個選項都是名詞，而 feature（特色）在講新產品的文章裡出現頻率很高，很容易第一眼就選它。這一格要往前讀一句，看作者剛剛講的是好事還是壞事。
四個選項都是名詞，可見這一格考的是語意，那就往前讀。前一句是 But silicon is expensive and the panels are heavy.（但矽很貴，而且面板很重。）——句首用 But 一轉，講的是傳統太陽能板的兩個缺點。本句是 Facing this ___ , engineers ... have developed a thin-film flexible solar panel.（面對這個……，工程師開發出薄膜可撓式太陽能板。）既然前面講的是問題、後面講的是為解決問題而開發的新東西，空格要填的當然是「難題」，填 challenge。
strength（優勢）：方向完全相反，如果矽的昂貴笨重是優勢，就沒有理由去開發新面板。feature（特色）：中性，說不出「需要被克服」的意思，與 Facing（面對）這個動詞也不搭——人不會「面對一個特色」。reaction（反應）：前一句講的是材料的性質，不是誰對誰的反應。
face a challenge（面對挑戰）、meet a challenge（迎接挑戰）、pose a challenge（構成挑戰）、a major strength（一大優勢）、a key feature（一項關鍵特色）、crystallized silicon（結晶矽）。
Solar panels can turn sunlight into electricity. Conventional solar panels are 16 crystallized silicon, the same material used in computer chips. But silicon is expensive and the panels are heavy. Facing this 17 , engineers at a Japanese company have developed a thin-film flexible solar panel. The new panel is not the first of its 18 , but it may be the most flexible—it bends like paper.
At one kilogram per square meter, this new type of panel weighs one tenth of conventional solar panels. 19 means it could be used in novel places, such as the roof of a tent, the walls of a building, or the top of a bus. Sheets of the material could be used to make portable, rollable battery chargers for mobile electronic 20 , like notebook computers or cellphones. As many countries are now pushing for green technology, the new flexible solar panels may spur a great demand.