Although Having Evolved Independently, the Tracheal Tubes of Mammals and Insects

Although having evolved independently, the tracheal tubes of mammals and insects are both supported by rigid tissues. The trachea of a mammal are supported by cartilage, and the tracheae of an insect are supported by chitin. Which of the following is a selective pressure that most likely led to the convergent evolution of these respiratory structures?

A) Both mammals and insects have similar oxygen needs.
B) When breathing air, there is a risk that trachea and tracheal tubes will collapse.
C) Insects and mammals both keep their internal temperature constant.
D) A decrease in environmental carbon dioxide made structural support necessary.