试题题干
WORD FORMATION
Complete each of the following sentences with the proper form of the word in brackets.
Asian food production has doubled through a 
of high-yielding crops, expanded farming area and greater intensification. (combine)
参考答案
试题解析
此处缺少名词。
a是冠词，of是介词，所以中间缺少名词。所以变combine为名词combination。a combination of...，意为...的结合。
句意：亚洲粮食产量通过高产作物、扩大农业面积和更大的集约化增长了一倍。