Hull's background in mathematics and engineering was demonstrated in the use of postulates and axioms in his system his invention of a machine to calculate correlations all of the choices are correct. his development of statistical analysis methods his description and explanation of behavior in mathematical equations

His backgrounds in mathematics and engineering was demonstrated in: 
- his development of statistical analysis methods
- his invention of a machine to calculate correlations,
- the issue of postulates and axioms in his system
- his descriptions and explanations of behavior in mathematical equations

Due to this characteristic, Clark L Hull managed to provide accurate data/measurements in studying the correlateon between motivation and behaviors and what caused them. Due to this findings,  his school of psychology dominated the field in 1940s.

The answer is congress