If a hiker is recommended to drink 24 ounces of water per hour, we first need to figure out how much water is consumed in 10 minutes.
1 hour = 60 minutes
In 10 minutes, the amount of water consumed would be:
\[ \frac{24 \text{ oz}}{60 \text{ min}} \times 10 \text{ min} = 4 \text{ oz} \]
This means that every 10 minutes, the hiker should drink 4 ounces of water from the canteen.
Since the amount of water in the canteen decreases when the hiker drinks, this change in amount should be described as a negative value.
Therefore, the change in the amount of water in the canteen every 10 minutes is -4 oz.
So, the correct answer is B) -4 oz.