Use the following processes to answer this question. I-Ribs move upward and outward II- Diaphragm relaxes…

Analyze the question: We need the process that is a direct result of the intercostal muscles contracting. This is about the mechanics of breathing (inspiration).

Concept: There are two sets of intercostal muscles between the ribs:

• External intercostal muscles contract during inhalation (inspiration).
• Internal intercostal muscles contract during forced exhalation.

In normal inspiration:

1. The external intercostal muscles contract.
2. The ribs move upward and outward.
3. The diaphragm contracts and flattens (it does not relax).
4. The volume of the thorax increases.
5. Pressure in the thorax falls, and air rushes into the lungs.

Solution, going through each process:

• I - Ribs move upward and outward: This is the direct effect of the intercostal muscles contracting. The muscles pull the rib cage up and out.
• II - Diaphragm relaxes: This is wrong for inspiration, because the diaphragm contracts then. Its relaxation is linked to expiration, and it is not caused by the intercostal muscles.
• III - Volume of thorax increases: This happens, but it is an indirect result. It follows from the ribs moving up and out together with the diaphragm flattening.
• IV - Air is forced out of the lungs: This is expiration, which does not result from contraction of the external intercostals.

The word "direct" is the key. The muscle contraction first moves the ribs, and the increase in thoracic volume follows from that movement.

Answer: A (I)

Exam tip: Follow the chain of events for inspiration: intercostals contract → ribs up and out → thorax volume increases → pressure drops → air enters. When a question says "direct result," choose the first step after the muscle action, not the later effects.