Question

(b) the daily amount of calories that a rat eats increases steadily from birth to about age 3 months. then, the amount levels off until about age 6 months, when it increases again.

Explanation:

To solve this, we analyze the description of the rat's calorie intake over time:

1. Initial Phase (Birth to 3 months): The daily calories increase steadily. This means the graph should have a positive - sloped line (rising from left to right) during this time.
2. Middle Phase (3 to 6 months): The daily calories level off. This corresponds to a horizontal line (constant y - value) on the graph.
3. Final Phase (After 6 months): The daily calories increase again. This means the graph should have another positive - sloped line (rising from left to right) after the horizontal segment.

Now let's analyze each graph:

• First graph (top - most):
• Starts at (0,0) (birth, 0 calories? Wait, actually, at birth, the rat does eat, but the key is the trend). It has a rising line (birth to 3 months), then a horizontal line (3 - 6 months), then a rising line (after 6 months). This matches the description.
• Second graph: It has a horizontal line first, then a falling line, then a horizontal line. Doesn't match (we need an initial rise, not a horizontal start).
• Third graph: It has a rising line, then a falling line. Doesn't match (we need a horizontal segment in the middle, not a fall).
• Fourth graph: It has a horizontal line, then a fall, then a rise. Doesn't match (initial trend should be a rise, not horizontal).

So the correct graph is the first one (the top - most option with the rising - horizontal - rising pattern).

Answer:

The first graph (the one with the line that rises, then is horizontal, then rises again)