Cytotoxic t cells recognize and kill host cells infected by viruses. they recognize these cells by the foreign antigen displayed on the host cell's:

The statement above is TRUE. 
There are two types of T cells; cytotoxic T cells and helpers T cells. Cytotoxic T cells are specialists in killing cells that are infected with virus or some other pathogens. T cells are antigen-specific  and they defend the body against infections. T cells have the capacity to eliminate pathogens that reside inside the host cells. 

Atp is is our little "pocket" of energy. of course, if you have too little, then it means you have too little energy, and you'll pass out. the way to not have enough, is to have no energy sources (glucose, fats, proteins). you can't have too many atp molecules. cycles like the krebs cycle produce it, but if you have too much of any substrate (or too little for that matter), the cycle stops and atp is no longer made (it stops until substrate levels are such that the process can go on). in any case, this is unlikely since atp is constantly hydrolyzed and remade, even while you're asleep. you won't have too much. if you have zero, you are dead or dying.