In the case of vocabulary use, grammar provides a pathway for learners to :

The correct option is combine lexical items into meaningful and communicative expressions.

Explanation:

Grammar provides the structural rules and frameworks that allow learners to organize individual words and phrases (lexical items) into coherent, meaningful, and communicative sentences and expressions.

Without grammar, vocabulary consists only of isolated words. By applying grammatical structures, language learners are able to connect these lexical items to convey clear messages, intentions, and complex ideas effectively in communication.