Identify the structure of the human heart which is a muscular chamber that pumps blood out of the heart and into the circulatory system.
a) atrium
b) ventricle
c) coronary artery
d) pulmonary artery

What is the relationship between absorbance of light and the rate of photosynthesis?

Select the correct answer from each drop-down menu. in an experiment, dr. travis examined the effects of calcium intake on osteoporosis, a condition that causes an increased risk of bone fractures. the amount of calcium is variable. the risk of bone fractures .

Which of the following statements about archaea and bacteria is true? a. neither is single-celled. b. they both have nuclear membranes. c. neither reproduces by binary fission. d. they both lack a nuclear membrane.