Answer:
about 5 billion years ago
Explanation:
Our solar system formed about 5 billion years a go from a dense cloud of interstellar gas and dust.
Answer:
A Car on the top of a hill
Explanation:
A Car on the top of the hill because The car isn't moving so it has potential energy NOT Kinetic
Selectively permeable (or semi permeable) means where for example a membrane can choose what material can pass through while others cannot. They control the in and out of materials.
This is because the membrane has tiny spaces, where only smaller molecules can pass through, other larger ones cannot.
Opportunistic infections are infections that occur more frequently and are more severe in people with weakened immune systems, including people with HIV.
