— What are the twin sisters doing?

— ___________________[ ]

A. They're joging.

B. She's jogging.

C. They're jogging.

当抵抗_________侵入的功能过强时，进入人体内的某些食物和药物会引起________。疫苗通常是用___________或____________的病原体制成的生物制品接种于人体，从而提高人体的抵抗力。