The temperature in a city was recorded at four different times during a day: at 6 AM, at 12 PM, at 6 PM, and at 12 AM. Which of the following statements best describes the trend shown in the line graph representing these temperature changes? 
The temperature continuously increased throughout the day.
The temperature continuously decreased throughout the day.
The temperature increased and then decreased.
The temperature remained relatively constant.
The temperature increased, then decreased, then increased again.
