4. What body systems are described in the concept map below? Gland
secretes
Hormone
Transported
by blood
Body responds and
changes
A. Circulatory and excretory
B. Endocrine and circulatory
C. Excretory and endocrine
D. Respiratory and excretory

the  frequency of a wave represents  the number of wavelengths that pass a specific point per second. the unit for  frequency  is hertz (hz).

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the principles and empirical processes of discovery and demonstration considered characteristic of or necessary for scientific investigation, generally involving the observation of phenomena, the formulation of a hypothesis concerning the phenomena, experimentation to test the hypothesis, and development of a conclusion that confirms, rejects, or modifies the hypothesis.