Now research shows that plants have a somewhat 21 problem.
答案：(A) similar
語意「植物也有某種『類似』的問題」（呼應前一句人類打噴嚏傳播疾病），similar（類似的）符合這種類比；miserable（悲慘的）、realistic（現實的）、temporary（暫時的）都不合。
這一格看起來很簡單，但容易錯在只讀了本句、沒有回頭看前一句。空格前有一個關鍵的小字 somewhat（有點、某種程度上）——這個字專門用來緩和語氣，通常出現在「類比」的場合：兩件事不完全一樣，但有幾分像。看到 somewhat，就該往前找「跟什麼像」。
前一句是 When a person sneezes, the droplets can spread diseases（人打噴嚏時，飛沫會傳播疾病）。本句 Now research shows that plants have a somewhat ___ problem（研究顯示植物也有某種 ___ 的問題）。下一句更直接：a plant's version of a sneeze（植物版的噴嚏）。「人會這樣，植物也會」——這是標準的類比句型，空格只能是 similar。
miserable（悲慘的）帶強烈情緒，科普說明文不會這樣形容一個傳播現象；realistic（現實的）用來形容想法或計畫是否務實；temporary（暫時的）與文章描述的持續傳播機制無關。
a similar problem（類似的問題）、be similar to（與……相似）、similarity（相似之處）、somewhat（有點、某種程度上）、spread diseases（傳播疾病）、from leaf to leaf（一片葉子傳到另一片）。
When a person sneezes, the droplets can spread diseases. Now research shows that plants have a somewhat 21 problem. Plant diseases can also spread through tiny water drops that jump off leaves— a plant's version of a sneeze. Scientists already knew earlier that wind and splashes of rainwater can move bacteria and other germs from leaf to leaf.
22 other possible transmission routes, researchers at Virginia Tech observed water drops on the leaves of wheat plants that were infected with leaf rust. They found that the sick plants could "sneeze" and 23 tiny water drops filled with leaf rust germs, spreading the disease to neighboring plants. The researchers noticed that small drops of water on the wheat leaves would move to combine and form a larger drop. As they were moving, the energy of the droplets in motion would be released. This energy allowed the water 24 into the air, which looked just like sneezing!
However, not all plants can sneeze. The ability is 25 to those with leaves that are hydrophobic, or repel water—a special feature that forces the liquid to move away when the leaf is exposed to it.