Systolic blood pressure is the pressure exerted by blood on artery walls when the heart contracts. The normal systolic blood pressure for a healthy person is approximately 120 mm Hg.
- If the systolic pressure is above 140 mm Hg, it indicates hypertension (high blood pressure).
- If it is below 90 mm Hg, it may indicate hypotension (low blood pressure).
Thus, the correct answer is \( \mathbf{(B) \text{120 mm Hg}} \).