The correct option is A.
The nature is organized in such a way that, one organism's waste is what the other organism will use as its own resources. For instance, during the process of photosynthesis, the oxygen that is produced as the by product of the photosynthesis process is what humans use to carry out their own breathing process.
In general, yes, the dorsal blood vessel of a worm be seen from the worm's exterior because a worm's "skin" is very thin. Although of course there are exceptions.
I am certain your answer is true.good luck
I would guess that the answer would be :'<span>These organisms dig more shallow burrows than they used to.</span>' If the crabs actively dig burrows, as many crab species do, and a layer of oil has persisted in the lower soil strata, it makes sense that the crabs would be reducing the depths of their burrows to avoid contact with the oil. The other possibility is that the crabs might might migrate to deeper waters, but this is less likely because the crabs would be evolved to utilise the intertidal zone.
