An Oscilloscope's Seconds/division Switch Is Set on 20 $\mu \mathrm { s } / \mathrm { cm }$

Multiple Choice

An oscilloscope's seconds/division switch is set on 20 $\mu \mathrm { s } / \mathrm { cm }$ . If the trace is 7.5 cm long, what is the period?

A) 150 $\mu \mathrm { s }$
B) 1.5
C) 5 $\mu \mathrm { s }$
D) 0.0015 s