When making a decision regarding treatment of sinus bradycardia or sinus tachycardia, the most important determinant is the patient's:

Which of the following substances is not likely to cross a placenta?

A. An ionized or water-soluble substance B. Tetracycline C. Nicotine D. Alcohol

Mechanical external compression devices are recommended:

A) By AHA 2015 guidelines as a preferred substitute for manual CPR B) Because patient ventilation is not required C) When high-quality manual compressions are not possible D) For short-term use only