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。