A friend is telling you that they tend to drink more at parties than they do at home. You ask about why and they tell you that though they enjoy their fifth and sixth drinks the same regardless of where they are. Based on the fact that it is free at the party and they have to pay to replace it at home, you can translate the statement into a verification of

Deep structure of the sentence

Explanation:

The deep structure also called a D- structure or the deep structure of the sentence in the grammar of the transformation structure of the sentence. It is a syntactic structure of the sentence. It is the structure that analyses and interpreted the sentence away. The deep structure of a sentence by the phrase structure rules.

There are some properties of a deep structure:

The relation of subjects and objects that are called the deep structure of a sentence. Lexical insertion occurs at this level. The transformation level occurs after this deep level.  Semantic interpretation occurs at this level.