After we made the improvement; there were only ______ as before. A．one-tenth defective products as many B．one-tenth as many defective products C．defective products one-tenth as many D．defective products as one-tenth many

步骤 1：分析句子结构
句子结构为：After we made the improvement; there were only ______ as before.
需要填入的成分是句子的主语和谓语动词后的宾语。

步骤 2：理解选项含义
A. one-tenth defective products as many
B. one-tenth as many defective products
C. defective products one-tenth as many
D. defective products as one-tenth many

步骤 3：分析选项语法
A. one-tenth defective products as many
- one-tenth和many都是限定词，不能同时出现在名词词组之前。
- 此选项语法错误。

B. one-tenth as many defective products
- one-tenth和many都是限定词，可以同时出现在名词词组之前。
- 此选项语法正确。

C. defective products one-tenth as many
- one-tenth和many都是限定词，不能同时出现在名词词组之前。
- 此选项语法错误。

D. defective products as one-tenth many
- one-tenth和many都是限定词，不能同时出现在名词词组之前。
- 此选项语法错误。

步骤 4：选择正确答案
根据语法分析，选项B是唯一语法正确的选项。