The free-radical theory states that aging is caused by damage to dna the body's lowered resistance to stress and disease biological constraints on cell division nutritional deficiencies

The correct answer would be the first option. The free-radical theory states that aging is caused by damage to DNA. This theory is a theory of aging which says that living organism would age because the cells would accumulate free radicals through out the life of the organism which would damage the cell. A free radical is any molecule or atom that contains an unpaired electron in its outer shell. These molecules can be formed by the interaction of oxygen with certain atoms. Once they are in the body, they start to damage certain components like the cell membrane or the DNA.

Neurotransmitters are messengers responsible for communication between neurons. they are released from synaptic vesicles and are received by receptors.  the communication is referred to as neurotransmission. the following statement is true about neurotransmitters: a. they're stored in synaptic vesicles in the axon.