The cartilaginous structures<span> that ring most mammalian tracheae are ... The </span>trachea<span> is</span>lined<span> with a moist mucous-membrane layer composed of </span>cells<span> containing small hairlike projections called </span>cilia<span>. ... </span>Such<span> outgrowths could </span>have<span> been useful to insects exposed by the drying up of a temporary aquatic.
IMPORTANT! * MARK AS BRAINLIEST </span><span>ANSWER !!!! *</span>
It's both! Scientists really can't agree on it.