Why tryptophan has difficulty getting into your brain and making you sleepy on its own

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 does natural resource management aim at ?

Which statement describe events that occur during interphase?