which expression represents purely real numbers and which expression represents non-real complex number?

Incomplete question. However, I provided some explanation about non-real complex numbers.

Explanation:

In Mathematics, the term complex numbers (non-real complex numbers) in simple terms refers to numbers that containing an imaginary addition to it.

For example, the numbers 3i, 3 + 5i, 3i/4 are non-real numbers because of the addition of an imaginary part which is denoted by 'i'.

While real numbers, on the other hand, are numbers that do not include an imaginary part; they stand on their own, such as whole numbers 0, 1, 2, 3, etc, rational numbers like 3/4, etc.

a) one student is chosen from classroom a, then a student is chosen from classroom b.  

step-by-step explanation:

independent events are ones in which the probability of one event does not affect the probability of the second event.

one student is chosen from classroom a; this does not affect the chances of choosing a student from classroom b.   this makes these independent events.

when one card is chosen from a standard deck and then set aside before a second card is chosen, the probability of the second card being chosen changes.   this makes them dependent events.

when one student is chosen from classroom a and then a second student is chosen from classroom a, the probability of choosing the second student changes.   this makes them dependent events.

when a letter is chosen from the alphabet and then a second letter is chosen, the probability of choosing the second letter changes.   this makes them dependent events.