Which concept emphasizes development resulting from ongoing bidirectional exchanges between heredity and all levels of the environment?

The number of times the heart beats each minute

A. is defined as stroke volume B. at rest is consistently lower in childhood than in adulthood C. is defined as heart rate D. is defined as stroke volume AND at rest is consistently lower in childhood than in adulthood E. at rest is consistently lower in childhood than in adulthood AND is defined as heart rate

__________ plays a critical role as a neurotransmitter that stimulates voluntary muscle movement directly at the junction between nerves and muscles

A) acetylcholine B) GABA C) dopamine D) endorphin