A teacher is reading the book, while reading he is focusing on vocabulary items, explaining the meanings of the words in the mother tongue of the learners. He explains the paragraph line by line in their native language. He is using method /approach in the class.

Correct option is D

A teacher explaining vocabulary items and meanings in the learners' mother tongue and translating paragraphs line by line is using the 'grammar translation method'. This method focuses on translating sentences and texts, learning grammar rules, and acquiring vocabulary. It often involves the use of learners' native language for explanation, which is characteristic of the approach described in the scenario.