Why is it said that the earthworm has a closed circulatory system?

The buildup of sediments where a river empties into a slow-moving or nonmoving body of water is known as a/an

What can be said about farmers in highly developed countries? a) they have little or no negative impact on the environment. b) they practice subsistence agriculture. c) they are able to incorporate polyculture into their farming practices. d) they utilize organic farming techniques on a regular basis. e) they rely on large amounts of energy from fossil fuels.

What if the yeast were extremely active and produced more than 100ml gas. would you know? why/why not