1. which statement concerning an ecosystem is correct?
(1) it can exist with or without a constant source of energy
input.
(2) it must contain consumers but can exist without
producers
(3) it involves interactions between biotic and abiotic
factors.
(4) it can exist on land, but it cannot exist in lakes, rivers,
or oceans.

african americans demonstrated their newly found freedom by relocating often in search of relatives whom they had been separated from during slavery. others established schools to educate freed people and they built institutions such as churches and political organizations to advocate for their rights.

it can be observed without changing the identity of the object.

it depends on what substance you're talking about as well as many other factors. in quantum mechanics, the observation of particles affects the observers ability to measure certain properties. for example: you can know the velocity of a particle, but you can't know it's position; or you can know it's position, but not it's velocity. it's like trying to find out where a grain of sand is by throwing other grains of sand at it. once you find out where it is, it's been moved. it's also like trying to find an answer to the question of whether or not a tree falling in a forest makes a sound if nobody is there to hear it. paradoxically, the only way to find out is to be there and hear it.

c) should be the answer.

c. orbital shape i hope this is correct