问题
选择题
They ___________to put their hearts into study..
A．have made their minds
B．have made their mind
C．have made up their minds
D．have made up their mind
答案
答案：C
题目分析：考查短语固定搭配。本题考查短语固定搭配make up one’s mind下定决心做某事。mind的数随物主代词的数而变化。句意：他们已经下定决心投身于学习中。故C正确。