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.
答案：(A) That
That 代替前面提到的整個概念（新面板重量只有傳統的十分之一），作句子主詞；What（不能這樣代替前述概念作主詞開頭）、There（存在句，不合makes的動詞結構）、Which（關係代名詞需要接在名詞後面）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。
四個選項都是很短的功能詞，而 What 與 Which 都是你熟悉的、能帶出子句的字，很容易先往那邊想。這一格要先數空格後面的成分——這一次成分是滿的。
先看空格後面：___ means it could be used in novel places。means 是動詞，所以空格是這個句子的主詞；而 means 後面的 it could be used in novel places 是完整的受詞子句，成分不缺。再看它要指什麼：前一句說 this new type of panel weighs one tenth of conventional solar panels（這種新面板的重量只有傳統面板的十分之一）。本句要說的是「這一點意味著它可以用在新奇的地方」——那個「這一點」指的是前面一整句話，用指示代名詞 That 就可以了。That 本身不進子句、不占任何成分，單純出現在主詞的位置回指前文。這一格與同一份考卷的第 21 題正好是一組對照，兩題把「數成分」這個判準的兩面都考了，等一下看第 21 題就會發現。
What：它必須帶出一個名詞子句，而且自己要在那個子句裡占一個位置（當主詞或受詞）；本句 means 後面的成分已經滿了，沒有位置給它。Which：關係代名詞，前面要有先行詞才能用，而本句空格出現在句首，前面隔著句號，沒有先行詞。There：只用在 there is／there are 這類存在句裡，當不了 means 的主詞。
That means …（這意味著……）、That is why …（那就是為什麼……）、in novel places（在新奇的地方）、one tenth of（十分之一）、weigh（重達）、novel（新奇的）。
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.