In which of the following situations will helper T cells be activated? when an antigen is displayed by a macrophage that engulfed a pathogen

when a cytotoxic T cell releases cytokines

when cytotoxic T cells come in contact with a tumor cell

when B cells respond to T-independent antigens

This is a typical grassland food web. it is also a small picture of an important cycle on earth: the carbon cycle. describe how the carbon gets into this food web. a) bacteria and fungi, the decomposers, recycle carbon from dead organisms. b) carbon is found in the grass and is passed from one level to the next in this food web. eliminate c) all living things give off carbon dioxide as a by-product of respiration and it is released into the atmosphere. d) plants use carbon dioxide as a reactant in photosynthesis, to make usable chemical energy in the form of a sugar.

What part of the cell membrane does not mix with water

Which statement is true about the two stars labeled in this diagram?