Let's analyze each of the statements based on the provided data regarding energy storage in humans.
### Statement 1: Blood is a primary location for energy storage.
From the data, the energy stored in free glucose in the blood is 40 kcal, which supports life for only a few minutes. This amount is relatively small compared to glycogen and lipids. Thus, saying that blood is a primary location for energy storage is not accurate as it only provides a very short-term supply of energy in critical situations.
### Statement 2: Fat molecules contain more energy-containing bonds than simple sugars.
The data shows that lipids (fats) have 9 kcal per gram, which is more than both free glucose in blood and glycogen, each of which have 4 kcal per gram. This indicates that fat molecules indeed contain more energy-containing bonds per gram compared to simple sugars. Therefore, this statement is true.
### Statement 3: A gram of glycogen has twice as much energy as a gram of fat.
Inspecting the table, we see that glycogen has 4 kcal per gram while lipids (fats) have 9 kcal per gram. Clearly, glycogen has less than half the energy per gram compared to fat. Hence, this statement is false.
### Statement 4: The human body stores approximately [tex]$1,000$[/tex] kcal of glucose.
Free glucose in the blood stores 40 kcal, and glycogen stores between 600 and 1600 kcal. Combining the average values of glycogen storage gives us a range of 640 to 1640 kcal. This indicates that the total glucose storage in the body is within the range that includes 1000 kcal but saying that it approximates to exactly 1000 kcal is somewhat misleading given the variability and range provided.
Given these analyses, the best conclusion based on the data provided is:
Fat molecules contain more energy-containing bonds than simple sugars.
