Answer: operon
Explanation:
An operon is a cluster of genes that are transcribed together to give a single messenger RNA (mRNA) molecule, which therefore encodes multiple proteins (Fig. 16.11). Such polycistronic mRNA is typically found in prokaryotes.
Because it allows only certain substances to permeate. If it was totally permeable that would be good enough to having no barrier as it would let everything though. Totally impermeable means that nothing would get through.
Answer: number 1 Your bronchioles are some of the smallest airways in your lungs. Inhaled air passes through tiny ducts from the bronchioles into elastic air sacs (alveoli).It A For two is A and for 3 is false