5. In a bilingual program at a junior high school in Toucheng, Ms. Kuo is teaching a social-studies-integrated English lesson on global migration patterns. She invites students to first brainstorm in Taiwanese or Mandarin with a partner about migration stories in their own families, then articulate the main themes to the whole class in English. Throughout the lesson, she welcomes contributions that weave English with Mandarin or Taiwanese, intentionally drawing on all three languages as resources to develop students' analytical understanding of migration concepts. A fellow teacher observing the class remarks that Ms. Kuo is merely tolerating language mixing because the students lack sufficient English proficiency, and warns that this practice contradicts the aims of the bilingual program. Which concept most accurately describes Ms. Kuo's pedagogical approach, and why is the fellow teacher's interpretation problematic？
(A)Mother tongue instruction, because local languages are being used to support content delivery.
(B)Sheltered instruction, because content is being linguistically simplified for language learners.
(C)Code-switching, because Ms. Kuo is alternating between languages for communicative ease.
(D)Translanguaging, because Ms. Kuo is strategically mobilizing students' full linguistic repertoire to construct meaning and content knowledge.