Researchers report in the journal Cell that reducing food intake protects cells against aging and age-related diseases. This phenomenon is likely linked to two enzymes—SIRT3 and SIRT4—in mitochondria, the cell’s powerhouse that is responsible for converting nutrients to energy. They found that a cascade of reactions triggered by lower caloric intake raises the levels of these enzymes, increasing the strength and efficiency of the cellular batteries. By invigorating the mitochondria, SIRT3 and SIRT4 extend the life of cells by preventing flagging mitochondria from developing tiny holes (or pores) in their membranes that allow proteins that trigger apoptosis, or cell death, to seep out into the rest of the cell. 6 Mark For Review6Which choice best describes the function of the underlined sentence in the text as a whole?A) It emphasizes that mitochondria are the most important components of the cell. B) It directly implicates mitochondria to be the primary key to extended lifespan. C) It stresses that mitochondria are the main sources of energy for the cell. D) It implies that mitochondria need to be recharged in order to function efficiently.