Identify the characteristic that plants, people, and flatworms have in common a. they all make their own food. b. they all use cellular respiration to obtain energy. c. they all use photosynthesis to obtain energy. d. they all ingest food.

The correct answer is option B, that is, they all use cellular respiration to obtain energy.  

Cellular respiration refers to a set of metabolic procedures and reactions, which occur in the cells of species to transform biochemical energy into ATP and then discharge waste products. The reactions taking place in respiration are catabolic, that is, dissociation of bigger molecules into smaller ones, and in the process liberating energy.  

The nutrients, which are generally utilized by plant and animal cells in the process of respiration are amino acids, sugar, and fatty acids, and the most usual oxidizing agent, that is, the electron acceptor is the molecular oxygen.