<h2><u>its is (A) skeletal and muscular</u> </h2><h2>because without skeletal ur body want be able to move also the muscular system do the sam but it give u strength to move it.</h2>
The first known single-celled organisms appeared on Earth about 3.5 billion years ago, roughly a billion years after Earth formed. More complex forms of life took longer to evolve, with the first multicellular animals not appearing until about 600 million years ago.
our water pipes, and the led in some water sources.
Answer:
There is little to no sunlight in the aphotic zone.
Explanation:
The aphotic zone is the deepest part of a lake/ocean, so no light is able to penetrate into those depths. Without light, photosynthetic organisms will not be able to undergo photosynthesis and will therefore not be able to survive.
