The expression that represents a complex number is the one in the second option.
[tex]\frac{2}{3} + \sqrt{-\frac{27}{28} }= \frac{2}{3} + \sqrt{\frac{27}{28} } i\\[/tex]
Which expression is a non-real complex number?
Remember that the complex number i is given by:
[tex]i = \sqrt{-1}[/tex]
So we have complex numbers when we have negative arguments inside of square roots.
In this particular case, the only option with a negative argument on a square root is on the second option:
[tex]\frac{2}{3} + \sqrt{-\frac{27}{28} } \\\\\frac{2}{3} + \sqrt{-1} *\sqrt{\frac{27}{28} } \\\\\frac{2}{3} + \sqrt{\frac{27}{28} } i\\[/tex]
We conclude that the correct option is the second one.
If you want to learn more about complex numbers:
https://brainly.com/question/10662770
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