Language skills are best learnt:

Concept: The integrated-skills approach to language pedagogy holds that listening, speaking, reading, and writing are interdependent processes, not isolated skills. Language is acquired most effectively when learners practise these skills together, around shared, meaningful, communicative tasks, rather than through isolated drills or the repeated practice of a single skill.

Application: When teaching a language, this means designing activities that combine listening, speaking, reading, and writing around a common theme or real-life communication task, so each skill reinforces the others — a listening or reading input feeds into discussion, which in turn feeds into writing. Dealing with the four skills in this connected, integrated manner builds stronger overall proficiency than developing them one at a time or through mechanical repetition.

Cross-check — why the other approaches fall short:

• Challenging, mechanical drills emphasise repeated practice of forms in isolation from meaningful communication, which does not transfer well to real language use.

• Focusing on only one skill at a time cuts the natural reinforcing links between listening, speaking, reading, and writing, slowing overall acquisition.

• Relying only on written tests and assignments exercises reading and writing but leaves out the listening and speaking practice that communicative competence needs.

So the approach that treats the four language skills together, in an integrated manner, is the one supported by established language-teaching pedagogy.