Which of these theories states that we are motivated by several needs, but the strongest source is the lowest unsatisfied need?

The answer the needs hierarchy theory or hierarchy of needs theory. This theory is developed by Abraham Maslow. This is a theory containing a five layer model of human needs, frequently portrayed as hierarchical levels within a pyramid. Maslow indicated that people are motivated to attain certain needs and that some needs take superiority over others. Our most basic need is for physical survival like food, water, and shelter and this will be the first thing that motivates our behavior. Once that level is satisfied the next level up is what motivates us, and so on.