Who put forth the concept of the Language Acquisition Device (LAD) for learning a language?

In the context of Lev Vygotsky's 'Zone of Proximal Development' (ZPD), a child:

The Theory of Universal Grammar was formulated by which of the following linguists?

After introducing 'tense forms' to grade 5 students, a teacher organizes a pair activity: Student A modifies a present-tense text into past tense and conveys it to Student B. Student B tries to reconstruct the original present tense text. Student A continuously refines the output based on Student B's feedback until successful. Which theory or hypothesis of second language acquisition does this activity MOST closely represent?