When cells such as white blood cells of a vertebrate engulf bacteria, the membrane transport mechanism used is ( ). A: receptor-mediated endocytosis B: active transport C: passive transport D: Phagocytosis E: exocytosis

下面哪些句型，通常被用来引出研究问题？ A: While XYZ is well documented, it remains unclear whether/why... B: Despite a large body of evidence for XYZ, the detailed mechanisms for ... remain to be elucidated. C: However, it remains to be investigated whether... D: ABC is a main mechanism used by all vertebrate to ...