27. A basketball left out in a cold night was observed to be slightly deflated the next morning.*1 pointBoyle's LawCharles' LawGay-Lussac's LawAvogadro's Law

The phenomenon described in the question is best explained by Gay-Lussac's Law. This law states that the pressure of a gas is directly proportional to its absolute temperature, provided its volume is kept constant.

Here's the step-by-step explanation:

1. During the night, the temperature drops. According to Gay-Lussac's Law, if the temperature of a gas decreases, its pressure should also decrease if the volume is constant.

2. However, the basketball's volume is not entirely constant. The skin of the basketball provides a flexible boundary for the gas inside.

3. As the pressure of the gas inside the basketball decreases (due to the drop in temperature), the gas will exert less force on the walls of the basketball.

4. This decrease in force causes the basketball to contract slightly, hence why it appears slightly deflated.

So, the correct answer is Gay-Lussac's Law.