How do snails see an invisible trail?

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.

Hershey and chase confirmed that dna, not protein, was the genetic material. how do the results of their two experiments support this conclusion?

How can we use spectral lines of light coming from the superclusters to identify which is receding from earth at the slowest rate.