To find out how much time Irina has for each question, we first need to convert the 3 hours she has into minutes. Since there are 60 minutes in each hour:
\[ 3 \text{ hours} \times 60 \text{ minutes/hour} = 180 \text{ minutes} \]
Now, to find out how much time she has for each question, we divide the total time by the number of questions:
\[ \frac{180 \text{ minutes}}{45 \text{ questions}} = 4 \text{ minutes/question} \]
So, Irina has 4 minutes to spend on each question.
The correct answer is 4 minutes.