Answer #34

The correct answer is D: Commercial contrast bubbles of the size needed to pass through the pulmonary capillary bed do not naturally resonate in the range of frequency used for diagnostic ultrasound. In fact, fortunately the natural resonant frequency of the bubbles at this size is exactly in the range picked up by diagnostic ultrasound (2 to 20 MHz). The typical contrast bubble size is 1-5 microns.

All of the other answers are correct.