BODY SYSTEMS<span>INTEGUMENTARY SYSTEM
MUSCULAR SYSTEM
SKELETAL SYSTEM
CIRCULATORY SYSTEM
NERVOUS SYSTEM
LYMPHATIC SYSTEM
RESPIRATORY SYSTEM
ENDOCRINE SYSTEM
DIGESTIVE SYSTEM
URINARY SYSTEM
REPRODUCTIVE SYSTEM
CELLSTISSUES
ORGANS
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Your answer is D, Rhizobium
This means that each dominant allele "adds" to the expression of the next dominant allele. Usually, traits are polygenic when there is wide variation in the trait. For example, humans can be many different sizes. Height is a polygenic trait, controlled by at least three genes with six alleles.
