The difficulty in using idioms appropriately lies first in the d

The difficulty in using idioms appropriately lies first in the difficulty of grasping the elusive and figurative meaning and then in the difficulty of determining the ( ) function of idioms.
【正确答案】：SYNTACTIC
【题目解析】：习语的使用困难首先在于掌握难懂的比喻意义，其次是难以确定习语的句法功能。