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Below is an ultrasound image of a fetus surrounded by amniotic fluid. Outside the dark amniotic fluid is the uterine wall. The uterine wall is bright throughout its cross section. What explains this? The acoustic impedance is spatially non-uniform within the uterine wall. The uterine wall strongly absorbs ultrasound energy The acoustic impedance is uniform within the uterine wall. The uterine wall has a higher acoustic impedance than the amniotic fluid. E. The uterine wall has a lower acoustic impedance than the amniotic fluid