choose the true sentence

To choose the true sentence, we need some sentences to evaluate. Let's consider the following options:

1. The Earth is flat.
2. The Earth orbits around the Sun.
3. Water boils at 100 degrees Celsius at sea level.
4. Oxygen is a noble gas.
5. Plants perform photosynthesis to produce food.

Now, let's analyze each sentence to identify the true one:

1. The Earth is flat - This statement is false. We know from scientific evidence that the Earth is not flat but is an oblate spheroid.
2. The Earth orbits around the Sun - This statement is true. The Earth revolves around the Sun in an elliptical orbit.
3. Water boils at 100 degrees Celsius at sea level - This statement is true. At sea level, water boils at 100 degrees Celsius.
4. Oxygen is a noble gas - This statement is false. Oxygen is a chemical element found in the air we breathe and is not a noble gas.
5. Plants perform photosynthesis to produce food - This statement is true. Plants convert sunlight, water, and carbon dioxide into energy-rich sugars through the process of photosynthesis.

Therefore, the true sentence among the options provided is: Water boils at 100 degrees Celsius at sea level.