#### Answer

true

#### Work Step by Step

RECALL:
In the complex number $a+bi$, $a$ is the real number part while $bi$ is the imaginary number part.
Note that when $b=0$, the complex number $a+bi$ becomes $a+oi=a$, which is a real number.
.
This means that the set of real numbers is a subset of the set of complex numbers.
Thus, the given statement is true.