Farah became pale after going to her father because________.
A：he didn’t allow her to go to Spain
B：she didn’t do well in her exams
C：she had to leave Purple Girls Club
D：he asked her to improve her grades
《十八世纪的产业革命》一书中写道：瓦特改良蒸汽机成功后，工厂主博尔顿要求买主只付出每架机器的制造和安装的费用，另外加上比使用同等马力的气压机所获得燃料上节省费的三分之一。此做法（ ）
将成语补充完整，并解释。
____ ____不舍
____。
