As per the definition of of Data Abstraction it has 2 parts and one part is possible in C but not the other one.

Its a way to define abstract data type objects which are different from all other types of objects and so structures is way to be doing that where you can define the objects which are different from the rest but the abstraction in the real sense does not come from just grouping the data but also it should define the behavior of the data as well and that is not directly possible in C and so data abstraction is not there in C language.