题目解析:
instigate: 教唆,鼓动,激起。A 是改进;B 是研究,调查;C 是缩窄;D 是引起,使…发生。所以 D 的 cause 引起正确,注意不要被 investigate 迷惑,只是长得像而已。对应原文:So admired were these pieces that they encouraged the development of earthenware made in imitation of porcelain and instigated research into the method of their manufacture. 原句说那些陶器非常惹人喜爱,促进了 earthenware 的发展,也 instigate 了制陶方法的研究,instigate 与原文的 encourage 并列,所以应该是鼓励之意。A 提升改善 B 调查 C 变窄均不正确。