Which of the following sentences are statements? Give reasons for your answer.
All real numbers are complex numbers.

(A) complex number is defined as a number of the form $a + bi$,where $a$ and $b$ are real numbers and $i = \sqrt{-1}$.
Any real number $x$ can be expressed as $x + 0i$.
Since every real number can be written in the form $a + bi$,the sentence 'All real numbers are complex numbers' is always true.
Therefore,it is a statement.