Fresh onions are available 21 yellow, red and white throughout their season, March through August.
答案：(C) in
【句型】available in + 顏色/種類 字詞搭配「有……顏色/種類可供選擇」；from／for／of 都不合。
available 在你腦中最常見的搭配大概是 available for（可供…之用）或 available to（某人可取得），所以看到後面接的是顏色，直覺就挑了 for。答對率只有 47%，鑑別度更只有 35，是這一年最低的一題——連平常表現不錯的人也大量失手。原因很單純：這一格考的是一個純粹的搭配習慣，沒有道理可以推，只能靠有沒有看過。
句子在說新鮮洋蔥有黃、紅、白三種顏色可選。英文要講「某樣商品有哪些顏色、尺寸或款式可選」，用的是 available in：available in three colors（有三種顏色）、available in all sizes（各種尺寸都有）（劍橋詞典）。這個 in 表示「以某種形式或款式呈現」，和 in red（穿紅色的）、written in English（用英文寫的）是同一個 in。這種題目沒辦法靠上下文推，只能靠平常累積，所以遇到 available 時，把它三個常見的搭配一起記起來最划算：available in（有…款式或顏色）、available to somebody（某人可取得）、available for something（可供…之用）。
from：表來源或起點，available from March 才是「從三月開始供應」；這一篇後面確實有 March through August，但那是時間不是顏色。for：available for 後面接用途或對象，例如 available for rent（可供出租）。of：available of 不是英文的說法。
be available in（有…顏色或款式可選）、be available to somebody（某人可取得）、be available for（可供…之用）、throughout the season（整個產季期間）、water content（含水量）、be divided into（分成…）。
Onions can be divided into two categories: fresh onions and storage onions. Fresh onions are available 21 yellow, red and white throughout their season, March through August. They can be 22 by their thin, light-colored skin. Because they have a higher water content, they are typically sweeter and milder tasting than storage onions. This higher water content also makes 23 easier for them to bruise. With its delicate taste, the fresh onion is an ideal choice for salads and other lightly-cooked dishes.
Storage onions, on the other hand, are available August through April. 24 fresh onions, they have multiple layers of thick, dark, papery skin. They also have an 25 flavor and a higher percentage of solids. For these reasons, storage onions are the best choice for spicy dishes that require longer cooking times or more flavor.