Concept:
Blood pressure is the pressure exerted by circulating blood on the walls of blood vessels.
Step 1: Understanding systolic blood pressure.
Systolic blood pressure is the pressure during ventricular contraction.
Step 2: Normal value.
The normal adult blood pressure is commonly written as:
\[
120/80\ \text{mm Hg}
\]
Here, \(120\ \text{mm Hg}\) is systolic pressure and \(80\ \text{mm Hg}\) is diastolic pressure.
Step 3: Checking options.
80 mm Hg is usually diastolic pressure.
100 mm Hg is lower than usual systolic value.
160 mm Hg indicates high systolic pressure.
120 mm Hg is normal systolic pressure.
\[
\boxed{120\ \text{mm Hg}}
\]