Answer:
D. By diffusion across a capillary wall
Explanation:
D is the best answer because gas exchange takes place in our lungs. Our lungs have alveoli which have a network of tiny blood vessels called capillaries, here the O2 diffuses the capillary wall to enter the bloodstream, and similarly CO2 diffuses out and we exhale it our from our lungs.
I am assuming you would recommend a specialist.
Characteristics of Lancelets:
Small
Elongated
Marine invertebrate
Lacks a jaw
No sense organs
Has a notochord
Example: Lamprey
Characteristics of Tunicates:
Marine invertebrate
Has an outer coat that is rubbery or hard
Has two siphons
Examples: sea squirts, salps
I hope this is the answer that you were looking for.