Gas exchange in humans — practice question

What sequence of changes occurs when we breathe in?

• Adiaphragm contracts $\rightarrow$ volume of thorax increases $\rightarrow$ pressure in lungs decreases
• Bdiaphragm contracts $\rightarrow$ volume of thorax increases $\rightarrow$ pressure in lungs increases
• Cdiaphragm relaxes $\rightarrow$ volume of thorax increases $\rightarrow$ pressure in lungs decreases
• Ddiaphragm relaxes $\rightarrow$ volume of thorax increases $\rightarrow$ pressure in lungs increases